Polymer electrolyte material, polymer electrolyte molded product using the polymer electrolyte material and method for manufacturing the polymer electrolyte molded product, membrane electrode composite, and solid polymer fuel cell

ABSTRACT

It is an object of the present invention to provide a polymer electrolyte material which has excellent proton conductivity even under the conditions of a low humidity or a low temperature and is excellent in mechanical strength and fuel barrier properties, and which moreover can achieve high output, high energy density and long-term durability in forming a polymer electrolyte fuel cell therefrom, and a polymer electrolyte form article using the same and a method for producing the same, a membrane electrode assembly and a polymer electrolyte fuel cell, each using the same. 
     The present invention employs the following means. Namely, the polymer electrolyte material of the present invention is a polymer electrolyte material including a constituent unit (A1) containing an ionic group and a constituent unit (A2) substantially not containing an ionic group, wherein a phase separation structure is observed by a transmission electron microscope and a crystallization heat measured by differential scanning calorimetry is 0.1 J/g or more, or a phase separation structure is observed by a transmission electron microscope and the degree of crystallinity measured by wide angle X-ray diffraction is 0.5% or more. Also, the polymer electrolyte form article, the membrane electrode assembly and the polymer electrolyte fuel cell of the present invention are characterized by being composed of such polymer electrolyte materials.

CROSS-REFERENCE TO RELATED APPLICATIONS

This present application is a divisional of U.S. patent application Ser.No. 14/304,643 filed on Jun. 13, 2014, which is a divisional of U.S.patent application Ser. No. 12/377,263 filed on Feb. 11, 2009, which isa national phase application of PCT International No. PCT/JP2007/065490filed on Aug. 8, 2007, which claims priority to Japanese PatentApplication No. 2006-219539, filed on Aug. 11, 2006, the contents ofeach of which are incorporated herein by reference in their entirety.

TECHNICAL FIELD

The present invention relates to a highly practical polymer electrolytematerial which has excellent proton, conductivity even under theconditions of a low humidity or a low temperature and can achieveexcellent mechanical strength, fuel barrier properties and long-termdurability, as well as a polymer electrolyte form article, a membraneelectrode assembly and a polymer electrolyte fuel cell, each using thesame.

BACKGROUND ART

A fuel cell is a kind of electric power supply capable of generatingelectric energy by electrochemically oxidizing a fuel such as hydrogenor methanol, and an intense interest has been shown towards the fuelcell, as a clean energy supply source, recently. Particularly, it isexpected that a polymer electrolyte fuel cell is widely used as adistributed power generation facility of comparatively small scale, anda power generator of mobile bodies such as automobile and marine vessel,because of such high standard operation temperature as about 100° C. andhigh energy density. Also, an intense interest has been shown towardsthe polymer electrolyte fuel cell as a power supply of portable mobileequipment and a portable device, and it is expected to install thepolymer electrolyte fuel cell in a cellular phone and a personalcomputer in place of a secondary cell such as nickel-hydrogen cell orlithium ion cell.

In the polymer electrolyte fuel cell, an intense interest has been showntowards a direct methanol type fuel cell in which methanol is directlysupplied as a fuel (hereinafter, referred to as DMFC), in addition to aconventional polymer electrolyte fuel cell (hereinafter, referred to asPEFC) using a hydrogen as a fuel. DMFC has such an advantage that thefuel is liquid and no reformer is used and, therefore, energy density ishigh and an operating time per one fueled of the portable device is verylong.

In the fuel cell, anode and cathode in which the reaction capable ofgenerating electricity occurs, and a polymer electrolyte membrane usingas a proton conductor between the anode and the cathode constitute amembrane electrode assembly (hereinafter abbreviated to MEA) and a cellcomprising separators and MEA interposed between the separators isformed as a unit. The polymer electrolyte membrane is mainly composed ofthe polymer electrolyte material. The polymer electrolyte material isalso used for a binder of an electrocatalyst layer or the like.

As required properties of the polymer electrolyte membrane, high protonconductivity is exemplified, first. Also, since the polymer electrolytemembrane functions as a barrier which prevents a direct reaction betweena fuel and oxygen, low fuel permeability is required. Particularly, in apolymer electrolyte membrane for DMFC in which an organic solvent suchas methanol is used as the fuel, methanol permeation is referred to asmethanol crossover (hereinafter sometimes abbreviated to MCO) and causesa problem such as decrease in cell output and energy efficiency. Asother required properties, resistance to solvents is also an importantproperty as long-term durability against a high concentration fuel inDMFC in which the high concentration fuel such as methanol is used.Other required properties include chemical stability for enduring astrong oxidizing atmosphere during operation of a fuel cell, andmechanical strength and physical durability for enduring thinning andcycling of swelling and drying.

As the material of the polymer electrolyte membrane, NAFION®(manufactured by DuPont Co.) as a perfluorosulfonic acid-type polymerhas widely been used. NAFION® is very expensive because it is preparedthrough multi-step synthesis, and also has a problem that fuel crossoveris large because of its cluster structure. Also, there were problemsthat mechanical strength and physical durability of the membrane formedby swelling and drying are lost because of poor resistance to hot waterand poor resistance to hot methanol, and that it cannot be used at hightemperature because of low softening point, and a problem such as wastedisposal after use and a problem that it is difficult to recycle thematerial.

Furthermore, there was a problem that since proton conductivity dependson a water content of the membrane, it is necessary to maintain a highhumidity condition to exert high power generation performance as a fuelcell and a load of a humidifier is increased. Also, below freezingpoint, there was also a problem that proton conductivity is largelyreduced because water in a conducting membrane concerning conductivityis frozen and therefore power generation becomes impossible.

To solve these problems, some studies on a polymer electrolyte materialcontaining a hydrocarbon-type polymer of a nonperfluoro-type polymer asa base have been made. As a polymer structure, particularly intensivestudy on an aromatic polyether ketone and an aromatic polyethersulfonehas been made in view of heat resistance and chemical stability.

For example, there have been proposed a sulfonated compound of apoorly-soluble aromatic polyetherether ketone (examples thereof includesuch as VICTREX® PEEK®, manufactured by VICTREX Co.) which is anaromatic polyetherketone (see, for example, non-patent document 1),polysulfone in a narrow sense as an aromatic polyethersulfone(hereinafter sometimes abbreviated to PSF) (examples thereof includeUDEL P-1700, manufactured by BP Amoco Polymers, Inc.), a sulfonatedcompound of polyethersulfone (hereinafter sometimes abbreviated to PES)(examples thereof include Sumikaexcel® PES, manufactured by SumitomoChemical Co., Ltd.) in a narrow sense (see, for example, non-patentdocument 2) and the like, but there were a problem that if a content ofthe ionic group is increased in order to enhance the protonconductivity, a prepared membrane swells and therefore fuel crossoversuch as methanol or the like is large, and a problem that since thepolymer electrolyte material is low in a cohesive force of a polymerchain, stability of a polymer higher-order structure is insufficient andmechanical strength and physical durability of a prepared membrane areinsufficient.

Also, in the sulfonated compound (for example, non-patent documents 1and 2) of an aromatic polyetherketone (hereinafter sometimes abbreviatedto PES) (examples thereof include VICTREX PEEK-HT, manufactured byVICTREX Co.), there was a problem that because its crystallinity ishigh, a polymer having the composition of low density of a sulfonic acidgroup becomes insoluble in a solvent, resulting in poor processabilitybecause of a remained crystal moiety. To the contrary, when the densityof the sulfonic acid group’ is increased so as to enhanceprocessability, the polymer is not crystalline and drastically swells inwater and, therefore, the membrane thus formed not only shows large fuelcrossover but also is insufficient in mechanical strength and physicaldurability.

Furthermore, there have been proposed an aromatic polyethersulfone blockcopolymer (for example, patent document 3) and an aromaticpolyetherketone block copolymer (for example, non-patent document 3 andpatent document 4). However, also in these copolymers, there was aproblem that polymers are brittle and low in structural stability sincethese polymers use an amorphous polymer such as a PES-type polymer or aPEK-type polymer having a bulky side chain as a base structure becauseof solubility constraint and membranes prepared are inferior indimensional stability, mechanical strength and physical durability.

As described above, the polymer electrolyte material according to priorart is insufficient as a measures for improving economic efficiency,processability, proton conductivity under the conditions of a lowhumidity or a low temperature, fuel crossover, mechanical strength andtherefore long-term durability, and there has never been obtained anindustrially useful polymer electrolyte material for a fuel cell.

-   Non-Patent Document 1: “Polymer”, 1987, vol. 28, 1009-   Non-Patent Document 2: Journal of Membrane Science, 83 (1993)    211-220-   Non-Patent Document 3: “Polymer”, 2006, vol. 47, 4132-   Patent Document 1: Japanese Unexamined Patent Publication (Kokai)    No. 6-93114.-   Patent Document 2: Published Japanese Translation No. 2004-528683 of    the PCT Application-   Patent Document 3: Japanese Unexamined Patent Publication (Kokai)    No. 2003-31232-   Patent Document 4: Published Japanese Translation No. 2006-512428 of    the PCT Application

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

In view of the above state of the art, it is an object of the presentinvention to provide a polymer electrolyte material which has excellentproton conductivity even under the conditions of a low humidity or a lowtemperature and is excellent in mechanical strength and fuel barrierproperties, and which moreover can achieve high output, high energydensity and long-term durability in forming a polymer electrolyte fuelcell therefrom, and a polymer electrolyte form article using the sameand a method for producing the same, a membrane electrode assembly and apolymer electrolyte fuel cell, each using the same.

Means for Solving the Problems

The present invention employs the following means so as to solve suchproblems. Namely, the polymer electrolyte material of the presentinvention is a polymer electrolyte material including a constituent unit(A1) containing an ionic group and a constituent unit (A2) substantiallynot containing an ionic group, wherein a phase separation structure isobserved by a transmission electron microscope and a crystallizationheat measured by differential scanning calorimetry is 0.1 J/g or more,or a phase separation structure is observed by a transmission electronmicroscope and the degree of crystallinity measured by wide angle X-raydiffraction is 0.5% or more. Also, the polymer electrolyte form article,the membrane electrode assembly and the polymer electrolyte fuel cell ofthe present invention are characterized by being composed of suchpolymer electrolyte materials.

Effects of the Invention

According to the present invention, it is possible to provide a polymerelectrolyte material which has excellent proton conductivity even underthe conditions of a low humidity or a low temperature and is excellentin mechanical strength and fuel barrier properties, and which moreovercan achieve high output, high energy density and long-term durability informing a polymer electrolyte fuel cell therefrom, and a polymerelectrolyte form article using the same and a method for producing thesame, a membrane electrode assembly and a polymer electrolyte fuel cell,each using the same.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail.

The present invention has intensively studied on the above problem,namely, a polymer electrolyte material which has excellent protonconductivity even under the conditions of a low humidity or a lowtemperature and is excellent in mechanical strength, resistance tosolvents and fuel barrier properties, and which moreover can achievehigh output, high energy density and long-term durability in forming apolymer electrolyte fuel cell therefrom, and found that protonconductivity performance of the polymer electrolyte material is largelyinfluenced by a phase separation structure of the polymer electrolytematerial, namely, an aggregation state of a constituent unit (A1)containing an ionic group and a constituent unit {A2) substantially notcontaining an ionic group and a configuration of the aggregation, andthat performance of fuel barrier properties, mechanical strength andlong-term durability of the polymer electrolyte material are largelyinfluenced by the stabilization of a polymer higher-order structure,namely, crystallinity or a crystalline state and an amorphous state of apolymer.

Namely, it was found that when the polymer electrolyte material is apolymer electrolyte material including the constituent unit (A1)containing an ionic group and the constituent unit (A2) substantiallynot containing an ionic group, wherein a phase separation structure isobserved by a transmission electron microscope and a crystallizationheat measured by differential scanning calorimetry is 0.1 J/g or more,or a phase separation structure is observed by a transmission electronmicroscope and the degree of crystallinity measured by wide angle X-raydiffraction is 0.5% or more, the polymer electrolyte material not onlyhas excellent proton conductivity and fuel barrier properties, but alsocan achieve resistance to solvents, high strength, high toughness and along-term durability through stabilization of a polymer higher-orderstructure, and can solve these problems at once.

In the polymer electrolyte material of the present invention, it isnecessary that a phase separation structure is observed by atransmission electron microscope. The polymer electrolyte material ischaracterized by having excellent proton conductivity even under theconditions of a low humidity or a low temperature by controlling thephase separation structure of the polymer electrolyte material, namely,an aggregation state of the constituent unit (A1) containing an ionicgroup and the constituent, unit (A2) substantially not containing anionic group and a configuration of the aggregation. The phase separationstructure can be analyzed visually or with such as a scanning electronmicroscope (SEM), a •transmission electron microscope (TEM) and anatomic force microscope (AFM), but in the present invention, thepresence or absence of the phase separation structure is determined by atransmission electron microscope (TEM).

Particularly, in the present invention, in order to clearly identify theaggregation state of the constituent unit (A1) containing an ionic groupand the constituent unit (A2) substantially not containing an ionicgroup, the polymer electrolyte material is observed by TEM after anionic group of the polymer electrolyte material is ion-exchanged withcesium by immersing the polymer electrolyte material in a 10 wt %ethanol solution of cesium acetate.

In the present invention, “A phase separation structure is observed” isdefined as a state in which a phase separation structure is observedwhen TEM observations is carried out at 50000-fold magnification and anaverage interlaminar distance or an average distance between particlesmeasured by image processing is 8 nm or more. An upper limit of theaverage interlaminar distance or the average distance between particlesis not particularly limited, but 5000 nm or. less is a practical valuein view of a balance between the distance and mechanical properties.Particularly, the average interlaminar distance or the average distancebetween particles is more preferably 10 nm or more and 2000 nm or less,and most preferably 15 nm or more and 200 nm or less. When the phaseseparation structure is not observed by a transmission electronmicroscope or the average interlaminar distance or the average distancebetween particles is less than 8 nm, it is not preferable since thecontinuity of an ionic channel may be deficient and ionic conductivitymay be low. Further, when the average interlaminar distance is more than5000 nm, it is not preferable since mechanical strength or dimensionalstability may become poor.

Further, the phase separation structure more preferably has anisotropyin which a direction of a membrane thickness is longer than a directionof a membrane surface from the viewpoint of ionic conductivity. Theanisotropy is preferably two times or more and more preferably threetimes or more. Further, from the viewpoint of constructing a protonconductive path, the phase separation structure furthermore preferablyhas a bicontinuous structure in which a constituent component containingan ionic group continues in a direction of a membrane thickness.

Observations of the phase separation structure of such polymerelectrolyte materials by TEM is carried out by a′ method described inExamples.

Since the polymer electrolyte material of the present invention ischaracterized by having crystallization capacity while having the phaseseparation structure, it is necessary that crystallinity is identifiedby differential scanning calorimetry (DSC) or wide angle X-raydiffraction. Namely, one aspect of the polymer electrolyte material ofthe present invention is a polymer electrolyte material in which acrystallization heat measured by differential scanning calorimetry is0.1 J/g or more (hereinafter, may be referred to as an aspect A), andthe other aspect is a polymer electrolyte material in which the degreeof crystallinity measured by wide angle X-ray diffraction is 0.5% ormore (hereinafter, may be referred to as an aspect B). In the presentinvention, both of the aspect A and the aspect B are preferable aspects,but particularly, the aspect A is more preferable from the viewpoint ofhigh toughness and durability.

In the present invention, “a polymer has crystallinity” means that thepolymer can be crystallized on heating temperature, has acrystallization capacity, or has already been crystallized. Also, theamorphous polymer means a polymer which is not a crystalline polymer, inwhich crystallization does not substantially proceed. Accordingly, evena crystalline polymer can be in an amorphous state as a polymer statewhen crystallization does not adequately proceed.

First, the aspect A of the polymer electrolyte material of the presentinvention will be described. In the aspect A of the polymer electrolytematerial of the present invention, it is necessary that thecrystallization heat AH per unit weight (g) of a dried polymer asmeasured by differential scanning calorimetry (DSC) is 0.1 J/g or more.As the differential scanning calorimetry (DSC), temperature modulationDSC can be more preferably used in point of measuring accuracy.Particularly, it is more preferable from the viewpoint of mechanicalstrength, long-term durability, resistance to hot methanol and fuelbarrier properties that AH is 2 J/g or more. Particularly, AH is morepreferably 5 J/g or more, still more preferably 10 J/g or more, and mostpreferably 15 J/g or more. The upper limit of ΔH is not specificallylimited, but is practically 500 J/g or less.

Here, a method for measuring crystallinity by differential scanningcalorimetry (DSC) will be described. Since a chemical structure and ahigher order structure (crystal and amorphous state) of the polymervaries as a result of crystallization, melting and thermal decompositionof the polymer, the crystallinity of the polymer electrolyte material ofthe present invention is evaluated type on whether a crystallizationtemperature is recognized in a first heating in the differentialscanning calorimetry or not and an area of the crystallization peak inheat flow-temperature chart of DSC. That is, in the aspect A of thepolymer electrolyte material of the present invention, it is necessarythat a crystallization temperature is recognized in the first heatingand AH is 0.1 J/g or more in the differential scanning calorimetry.

In case the polymer is thermally decomposed, after preliminarilyconfirming a thermal decomposition temperature of the polymer bythermogravimetry/differential thermal (TG-DTA), the presence or absenceof a crystallization temperature is confirmed during heating thetemperature which is the thermal decomposition temperature or lower. Incase a crystallization temperature is recognized at the temperaturewhich is the thermal decomposition temperature or higher, there is apossibility that the chemical structure of the polymer varies, andtherefore it cannot be decided that the polymer had crystallizationcapacity.

The polymer electrolyte material, in which a crystallization temperatureis recognized in the first heating in the differential scanningcalorimetry, means that it has crystallization capacity. In a polymerelectrolyte material composed of an amorphous polymer, thecrystallization temperature is not recognized in the differentialscanning calorimetry. As the polymer electrolyte material of the presentinvention, the aspect A having an amorphous moiety, in whichcrystallization proceeds through heating, is a preferable example. Theremay be cases where by leaving the amorphous moiety in whichcrystallization proceeds through heating, the polymer electrolytematerial not only has excellent proton conductivity and fuel barrierproperties, but also can achieve extremely excellent resistance tosolvents, mechanical strength and physical durability.

Confirmation of the presence or absence of crystallization temperatureand measurement of crystallization heat of such an ionicgroup-containing block copolymer by temperature modulation DSC isperformed by a method described in Examples. A thermal decompositiontemperature is preferably confirmed separately bythermogravimetry/differential thermal or the like.

The crystallization temperature is recognized in an irreversible processand is recognized at a temperature of a glass transition temperature orhigher and a melting temperature or lower as a temperature.Crystallization heat can be calculated from the area of thecrystallization peak in heatflow-temperature chart of DSC. In case of apolymer electrolyte material having a sulfonic acid group, thecrystallization temperature is close to a thermal decompositiontemperature or a melting temperature and the high temperature of thecrystallization temperature may be influenced by decomposition ormelting. Therefore, in the present invention, the value, which isobtained by doubling heat from the low temperature to a peak top, isdefined as crystallization heat.

Next, the aspect B of the polymer electrolyte material of the presentinvention will be described. In the aspect B of the polymer electrolytematerial of the present invention, it is necessary that the degree ofcrystallinity measured by wide angle X-ray diffraction is 0.5% or more.A degree of crystallinity of the polymer electrolyte material of thepresent invention can be evaluated by the crystallinity measured by wideangle X-ray diffraction, and particularly, from the viewpoint ofdimensional stability, mechanical strength and long-term durability, thedegree of crystallinity is more preferably 3% or more, and furthermorepreferably 5%′ or more. The upper limit of the degree of crystallinity,is not particularly limited, but is practically 50% or less. When thedegree of crystallinity is less than 0.5% and the crystallization heatmeasured by DSC is less than 0.1 J/g, it is not preferred because apolymer is amorphous, dimensional stability may be insufficient becauseof unstable structure and long-term durability may be insufficientbecause of insufficient toughness.

The case where the crystallization temperature is not recognized in thefirst heating in the differential scanning calorimetry can be separatedspecifically into the case where the polymer is amorphous without havingcrystallinity and the case where the polymer has already beencrystallized. The polymer electrolyte material already crystallizedbecomes the aspect B of the polymer electrolyte material of the presentinvention and exhibits the degree of crystallinity, measured by wideangle X-ray diffraction, of 0.5% or more. However, in a polymerelectrolyte material composed of an amorphous polymer, it is impossibleto attain sufficient dimensional stability, mechanical strength,physical durability, fuel barrier properties and resistance to solventsbecause its structure is unstable, and it is impossible to achieve ahigh energy capacity or long-term durability in using the polymerelectrolyte material in the fuel cell.

The measurement of the degree of crystallinity by wide angle X-raydiffraction of such polymer electrolyte materials is performed by amethod described in Examples.

Preferable examples of the polymer electrolyte material of the presentinvention, whose phase separation structure is observed by TEM, includesuch as a block copolymer composed of a block (B1) containing an ionicgroup and a block (B2) substantially not containing an ionic group, apolymer alloy or a polymer mixture composed of a polymer containing anionic group and a polymer substantially not containing an ionic group,and a polymer containing an ionic group in either a main chain or a sidechain, but the polymer electrolyte material can be used without beinglimited to these.

Among these polymers, a block copolymer composed of a block (B1)containing an ionic group and a block (B2) substantially not containingan ionic group is more preferable as the polymer electrolyte material ofthe present invention, and a ratio W1/W2 of a molar amount W1 of the B1to a molar amount W2 of the B2 is more preferably 0.2 or more and 5 orless from the viewpoint of a balance between proton conductivity andmechanical properties or durability, furthermore preferably 0.25 or moreand 4 or less, and most preferably 0.33 or more and 3 or less. When theratio W1/W2 is less than 0.2 or more than 5, it is not preferablebecause an effect as a block copolymer becomes insufficient and theblock copolymer become deficient in proton conductivity, dimensionalstability or mechanical properties.

In addition, in the present invention, it is stated that the block (B2)does not substantially contain an ionic group, but the block (B2) maycontain a small amount of ionic groups within a range which does notaffect adversely an effect of the present invention, particularlycrystallinity.

In the present invention, the block copolymer refers to a blockcopolymer composed of two or more kinds of blocks. Also, the block inthe present invention is a partial structure of the block copolymer, andcomprises one kind of a repeating unit or a combination of a pluralitykinds of repeating units, and refers to those having a formula weight of2000 or more. Furthermore, the domain means a cluster made ofaggregation of similar blocks in one or a plurality of polymer chains.

Examples of the ionic group-containing block copolymer to be used forthe present invention include such as a block copolymer formed byreacting an ionic group-containing monomer and a monomer not containingan ionic group separately to form an ionic group-containing block and/ora block not containing an ionic group and then reacting these blocks, ablock copolymer formed by reacting an ionic group-containing monomer anda polymer not containing an ionic group, a block copolymer formed byreacting a monomer not containing an ionic group and an ionicgroup-containing polymer, and furthermore a block copolymer formed byforming a block taking advantage of the difference in reactivity betweenmonomers. Further, it is also possible that after obtaining a blockcopolymer having different reactivities, an ionic group is selectivelyintroduced into only a highly reactive site.

When two or more kinds of block chains which are immiscible with oneanother, namely, a block copolymer, in which a block (B1) containing anionic group and a block (B2) substantially not containing an ionic groupform one polymer chain linked by a covalent bond, is employed, it ispossible to control an arrangement of chemically different components ona nanoscale to a microscale. In the block copolymer, by short-rangeinteraction generated from the incompatibility between chemicallydifferent blocks, the copolymer is phase separated into regions(nanometer scaled (nano order) structure) comprising each block chainbut each microdomain is arranged keeping a specific order by virtue oflong-range interaction generated from a covalent bond between blockchains. A structure created by aggregation of microdomains comprisingeach block chain is referred to as a microphase separation structure.

A channel structure formed in a membrane by an ionically conductivecomponent is thought to be extremely important for ionic conduction.From the view that ions are transferred through a channel, a spatialarrangement of an ionic conduction site in the membrane becomesimportant. It is one of the objects of the present invention to attain apolymer electrolyte membrane exhibiting excellent ionic conductivity bycontrolling the spatial arrangement of an ionic conduction site in themembrane.

By adjusting a block length, a packing property, polarity, rigidity andhydrophilicity/hydrophobicity of the ionic group-containing blockcopolymer used for the present invention, it is possible to control theprocessability of the polymer electrolyte material and the polymerelectrolyte form article composed thereof, a size of the domain,crystallinity/noncrystallinity and fuel crossover, durability,resistance to solvents and mechanical characteristics.

However, when conventional aromatic polyethersulfone block copolymer oraromatic polyetherketone block copolymer is used as a polymerelectrolyte material, there were a problem that if a content of theionic group of the block copolymer is increased in order to enhance theproton conductivity under the conditions of a low humidity or a lowtemperature, a membrane swells significantly because of the aggregationof ionic groups and therefore fuel crossover such as methanol or thelike is large, and a problem that since the polymer electrolyte materialis low in a cohesive force of polymer chains, stability of a polymerhigher-order structure is insufficient and dimensional stability of amembrane, mechanical strength and physical durability are insufficient.

Further, the ionic group-containing block copolymer, in which similarblocks aggregate to form a domain, could not be used as a polymerelectrolyte material because processability becomes poor if acrystalline block exists.

On the other hand, the polymer electrolyte material of the presentinvention could control noncrystallinity/crystallinity throughintroduction of a protective group/deprotection, enhance the stabilityof a higher-order structure of the polymer electrolyte material througha pseudo-crosslinking effect by imparting crystallinity to the ionicgroup-containing block copolymer to be used, and achieve excellentdimensional stability, fuel barrier properties, mechanical strength andphysical durability while having excellent proton conductivity under theconditions of a low humidity or a low temperature. That is, the domainformed by aggregation of the block (B1) containing an ionic group playsa role of enhancing proton conductivity and the domain formed byaggregation of the block (B2) substantially not containing an ionicgroup plays a role of enhancing performance of dimensional stability,fuel barrier properties, mechanical strength and long-term durability bya pseudo-crosslinking effect by crystal. That is, the present inventionforms a phase separation structure by blocking the sites havingdifferent functions of ionic conductivity and crystallinity. Theionically-conductive block exhibits excellent proton conductivity byconstructing an ionically-conductive path, and the crystalline blockforms a crystal structure which is more robust than a random copolymer,and by this functional separation, the present invention achievescompatibility between a power generating property and durability.

Next, the ionic group-containing block copolymer used in the polymerelectrolyte material of the present invention will be describedspecifically. The ionic group-containing block copolymer used for thepresent invention is more preferably a hydrocarbon-type polymer from theviewpoint of crystallinity and mechanical strength. An ionicgroup-containing hydrocarbon-type polymer referred to in the presentinvention means a polymer having an ionic group other than aperfluoro-type polymer.

As used herein, a perfluoro-type polymer refers to a polymer in whichmost of or all of hydrogen of alkyl groups and/or alkylene groups in thepolymer are substituted with a fluorine. In the present specification, apolymer, in which 85% or more of hydrogen of alkyl groups and/oralkylene groups are substituted with a fluorine, is defined as aperfluoro-type polymer.

Typical examples of a perfluoro-type polymer having an ionic group ofthe present invention include commercialized products such as NAFION®manufactured by DuPont Co., Flemion® manufactured by Asahi Glass Co.,Ltd. and Aciplex® manufactured by Asahikasei Corporation. Structures ofthese perfluoro-type polymers having such an ionic group can berepresented by the following formula (N1):

In the formula (N1), n1 and n2 each independently represents a naturalnumber; and k1 and k2 each independently represents an integer of 0 to5.

In these perfluoro-type polymers having an ionic group, since ahydrophobic moiety and a hydrophilic moiety in the polymer form a definephase structure, a channel of water referred to as a cluster is formedin the polymer in a state of containing water. In this channel of water,fuel such as methanol readily moves, and therefore, it cannot beexpected to reduce fuel crossover. Further, crystallinity is notrecognized because of a bulky side chain and therefore it is notpreferable.

The ionic group-containing block copolymer to be used for the presentinvention is more preferably a polymer having an aromatic ring in a mainchain among hydrocarbon-type polymers from the viewpoint of mechanicalstrength, physical durability and chemical stability. That is, a polymerhaving an aromatic ring in a main chain, which has an ionic group, ismore preferable. A structure of the main chain is not particularlylimited as long as it has an aromatic ring in a main chain, and forexample, those having sufficient mechanical strength and physicaldurability, which are used as an engineering plastic, are preferable.

Specific examples of the polymer having an aromatic ring in a main chainto be used for an ionic group-containing block copolymer includepolymers containing at least one of constituent components such aspolysulfone, polyethersulfone, polyphenylene oxide, polyaryleneether-type polymer, polyphenylene sulfide, polyphenylene sulfidesulfone, polyparaphenylene, polyarylene-type polymer, polyaryleneketone,polyether ketone, polyarylene phosphinoxide, polyether phosphinoxide,polybenzoxazole, polybenzothiazole, polybenzimidazole, polyamide,polyimide, polyetherimide and polyimidesulfone.

As used herein, polysulfone, polyethersulfone and polyether ketone aregeneric names of polymers having a sulfone bond, an ether bond and aketone bond in the molecular chain and include, for example, polyetherketoneketone, polyetherether ketone, polyetherether ketoneketone,polyether ketone ether ketoneketone, and polyether ketone sulfone, butit is not intended to limit a specific polymer structure.

Among the above polymers having an aromatic ring in a main chain,polymers such as polysulfone, polyethersulfone, polyphenylene oxide,polyarylene ether-type polymer, polyphenylene sulfide, polyphenylenesulfide sulfone, polyarylene ketone, polyether ketone, polyarylenephosphinoxide, and polyether phosphinoxide are preferable in view ofmechanical strength, physical durability, processability and resistanceto hydrolysis.

Specific examples thereof include polymers containing an aromatic ringin a main chain, which have a repeating unit represented by thefollowing general formula (T1):

Wherein Z¹ and Z² represent an organic group containing an aromatic ringand each of Z¹ and Z² may represent two or more kinds of groups, and atleast a portion of at least one kind of Z¹ and Z² has an ionic group; Y¹represents an electron-withdrawing group; Y² represents oxygen orsulfur; and a and b each independently represents 0 or a positiveinteger, provided that a and b does not simultaneously represent 0.

Among the polymer comprising a repeating unit represented by the generalformula (T1), which has an aromatic ring in a main chain, a polymercomprising repeating units represented by the general formulas (T1-1) to(T1-6) is more preferable in view of resistance to hydrolysis,mechanical strength, physical durability and production cost. Among thepolymers comprising these repeating units, in view of mechanicalstrength, physical durability and production cost, an aromaticpolyether-type polymer′ in which Y2 is 0 is more preferable, and apolymer comprising a repeating unit represented by the general formula(T1-3), namely, an aromatic polyether ketone-type polymer, in which Y¹is a —CO— group and Y² is 0, is most preferable.

Wherein Z¹ and Z² represent an organic group containing an aromatic ringand each of Z¹ and Z² may represent two or more kinds of groups, and atleast a portion of at least one kind of Z¹ and Z² has an ionic group;and a and b each independently represents 0 or a positive integer,provided that a and b does not simultaneously represent 0.

An organic group as Z¹ and Z² is preferably a phenylene group, anaphthylene group, or a biphenylene group. These groups include a groupcontaining an ionic group. Further, these groups may be substituted witha group other than the ionic group, but nonsubstituted groups are morepreferable in point of imparting crystallinity. Z¹ and Z² arefurthermore preferably a phenylene group and a phenylene group having anionic group, and most preferably a p-phenylene group and a p-phenylenegroup having an ionic group.

Preferable examples of the organic group represented by R^(p) in thegeneral formula (T1-4) are a methyl group, an ethyl group, a propylgroup, an isopropyl group, a cyclopentyl group, a cyclohexyl group, anorbornyl group, a vinyl group, an allyl group, a benzyl group, a phenylgroup, a naphthyl group, and a phenylphenyl group. In view of industrialavailability, R^(p) is most preferably a phenyl group.

In the present invention, the aromatic polyether type polymer refers toa polymer which includes ether bonds as a form to bond, with aromaticring units to one another in a polymer mainly composed of aromaticrings. The examples of chemical bonding such as a direct bond, ketone,sulfone, sulfide, various alkylenes, imide, amide, ester and urethane,which are commonly used for forming an aromatic polymer, may exist inaddition to the ether bond. It is preferred that one or more ether bondsexist per repeating unit of a principal constituent component. Thearomatic ring may include, in addition to the hydrocarbon-type aromaticring, a hetero ring. Also, an aliphatic unit may partially constitutethe polymer, along with the aromatic ring unit. The aromatic unit mayhave optional substituents, for example, a hydrocarbon-type group suchas alkyl group, a halogen group, a nitro group, a cyano group, an aminogroup, a halogenated alkyl group, a carboxyl group, a phosphonic acidgroup, and a hydroxyl group.

As used herein, the aromatic polyether ketone-type polymer is a genericname of a polymer having at least an ether group and a ketone group inthe molecular chain and includes such as polyether ketone, polyetherketoneketone, polyetherether ketone, polyetherether. ketoneketone,polyether ketone ether ketoneketone, polyether ketone sulfone, polyetherketone phosphine oxide, and polyether ketone nitrile, and is not limitedto a specific polymer structure. The aromatic polyether ketone-typepolymer containing phosphine oxide or nitrile in large quantity may haveinsufficient solubility in a solvent in the ionic group-containingpolymer having a protective group, and the aromatic polyetherketone-type polymer containing sulfone in large quantity may haveinsufficient crystallinity, resistance to solvents such as resistance tohot methanol and resistance to hot water.

Next, preferable examples of the block (B2) substantially not containingthe ionic group to be used in the polymer electrolyte material of thepresent invention will be exemplified specifically.

In the block (B2) to be used in the polymer electrolyte material of thepresent invention, an aromatic polyether ketone (PEK)-type polymer,namely, a polymer, which comprises a constituent unit represented by thefollowing general formula (Q1) and does not substantially contain theionic group, is particularly preferable in that it exhibitscrystallinity because of its good packing and very strong intermolecularcohesive force, and has a property of being insoluble in a commonsolvent:

Z¹ and Z² in the general formula (Q1) represent a divalent organic groupcontaining an aromatic ring and each of Z¹ and Z² may represent two ormore kinds of groups but does not contain an ionic group; and a and beach independently represents a positive integer.

In the block (B2) to be used in the polymer electrolyte material of thepresent invention, a small amount of ionic group may be contained withina range which does not affect adversely an effect of the presentinvention, particularly crystallinity.

An organic group as Z¹ and Z² in the general formula (Q1) is morepreferably a phenylene group for Z¹ and at least one selected from thefollowing general formulas (X-1), (X-2), (X-4) and (X-5) for Z². Also,these groups may be substituted with a group other than the ionic group,but nonsubstituted groups are more preferable in point of impartingcrystallinity. Z¹ and Z² are more preferably a phenylene group, and mostpreferably a p-phenylene group.

the groups represented by the general formula (X-1), (X-2), (X-4) or(X-5) may be optionally substituted with a group other than the ionicgroup.

Preferable specific examples of the constituent unit represented by theabove general formula (Q1) include such as constituent units representedby the following general formulas (Q2) to (Q7), but it is not limited tothese constituent units, and it can be appropriately selected inconsideration of crystallinity or mechanical strength. Particularly, theconstituent unit represented by the above general formula (Q1) is morepreferably a constituent unit represented by the following generalformulas (Q2), (Q3), (Q6) and (Q7), and most preferably the followinggeneral formulas (Q2) and (Q7) in point of crystallinity and productioncost:

the general formulas (Q2) to (Q7) are all shown in the form of a bond ata para-position, but they may include the form of a bond at anotherposition such as an ortho-position or a meta-position as long as theyhave crystallinity. However, the para-position is more preferable fromthe viewpoint of crystallinity.

Next, preferable examples of the block (B1) containing the ionic groupto be used in the polymer electrolyte material of the present inventionwill be exemplified specifically. In the polymer electrolyte material ofthe present invention, the block (B1) has the-ionic group to form adomain, and whereby, a polymer electrolyte material or a polymerelectrolyte membrane can exhibit high proton conductivity in wide useconditions.

The ionic group to be used in the polymer electrolyte material of thepresent invention is preferably an atomic group having negative chargeand a group having a proton exchange capability. As the functionalgroup, a sulfonic acid group, a sulfoneimide group, a sulfuric acidgroup, a′ phosphonic acid group, a phosphoric acid group, and acarboxylic acid group are preferably used. As used herein, the sulfonicacid group means a group represented by the following general formula(f1), the sulfoneimide group means a group represented by the followinggeneral formula (f2) [in the general formula, R means an atomic group],the sulfuric acid group represents a group represented by the followinggeneral formula (f3), the phosphonic acid group means a grouprepresented by the following general formula (f4), the phosphoric acidgroup means a group represented by the following general formula (f5) or(f6), and the carboxylic acid group means a group represented by thefollowing general formula (f7).

Such an ionic group includes the case where the functional groups (f1)to (f7) are in the form of a salt. Examples of the cation, which formsthe salt, include any metal cation, and NR₄ ⁺ (R is an any organicgroup). In case of a metal cation, its valence is not specificallylimited and any metal cation can be used. Preferable′ specific examplesof the metal ion include ions of Li, Ma, K, Rh, Mg, Ca, Sr, Ti, Al, Fe,Pt, Ru, Ir, and Pd. Particularly, as the ionic group-containing blockcopolymer to be used for the present invention, Na, K, and Li, which areinexpensive and are easily capable of proton substitution, arepreferably used.

Two or more kinds of these ionic groups can be contained in the polymerelectrolyte material, and there may be cases where a combination ofthese ionic groups is more preferable. This combination is appropriatelydetermined depending on a structure of a polymer. Among these ionicgroups, it is more preferable to have at least a sulfonic acid group, asulfoneimide group, and a sulfuric acid group in view of high protonconductivity, and it is most preferable to have at least a sulfonic acidgroup in view of resistance to hydrolysis.

When the polymer electrolyte material of the present invention has asulfonic acid group, in view of proton conductivity and fuel barrierproperties, the density of the sulfonic acid group thereof is preferablyfrom 0.1 to 5.0 mmol/g, more preferably from 0.3 to 3 mmol/g, and mostpreferably from 0.5 to 2.5 mmol/g. By setting the density of thesulfonic acid group at 0.1 mmol/g or more, conductivity, namely, outputperformance can be maintained, and by setting the density of the •sulfonic acid group at 5 mmol/g or less, sufficient fuel barrierproperties, wet mechanical strength and long-term durability can beobtained in case of using as an electrolyte membrane for a fuel cell.

Particularly, from the viewpoint of balance between proton conductivityand mechanical strength or long-term durability, more preferably, thedensity of the sulfonic acid group of the block (B1) containing an ionicgroup is 1.7 to 5.0 mmol/g and the density of the sulfonic acid group ofthe block (B2) substantially not containing an ionic group is 0 to 0.5mmol/g. From the viewpoint of balance between proton conductivity andmechanical strength or long-term durability, the density of the sulfonicacid group of the block (B1) containing an ionic group is furthermorepreferably 3.0 to 4.5 mmol/g, and most preferably 3.5 to 4.0 mmol/g.From the viewpoint of balance between proton conductivity and mechanicalstrength or long-term durability, the density of the sulfonic acid groupof the block (B2) substantially not containing an ionic group isfurthermore preferably 0 to 0.2 mmol/g, and most preferably 0 mmol/g.

When the density of the sulfonic acid group of the block (B1) containingan ionic group is less than 1.7 mmol/g or more than 5.0 mmol/g, it isnot preferable because conductivity may be insufficient, or mechanicalstrength or dimensional stability may be deficient. Further, when thedensity of the sulfonic acid group of the block (B2) substantially notcontaining an ionic group is more than 0.5 mmol/g, it is not preferablebecause a phase separation structure becomes imprecise and conductivitymay be deficient.

As used herein, the density of the sulfonic acid group is the number ofmols of sulfonic acid groups introduced per unit dried weight of thepolymer electrolyte material or the polymer electrolyte membrane, and asthe value of the density increases, a degree of sulfonation increases.The density of the sulfonic acid group can be measured by elementalanalysis or acid-base titration. Among these methods, it is preferablethat the density is calculated from a S/C ratio using an elementalanalysis method because of ease of the measurement. However, when thepolymer electrolyte membrane contains a sulfur other than the sulfonicacid group, it is also possible to determine the ion-exchange capacityby a acid-base titration method. The polymer electrolyte material andthe polymer electrolyte membrane of the present invention, as describedlater, include an. aspect as a complex comprising an ionicgroup-containing block copolymer used for the present invention andother components, and in this case, the density of the sulfonic acidgroup is determined based on the total amount of the complex.

The procedure of the acid-base titration is carried out as follows. Themeasurement is carried out three or more times and the obtained valuesare averaged.

(1) A sample is ground by a mill and screened through a net sieve #50and the particles passed through the net sieve is used as a measuringsample.(2) A sample tube (with a cap) is weighed by precision balance.(3) About 0.1 g of the sample obtained in (1) is put in the sample tubeand vacuum-dried at 40° C. for 16 hours.(4) The sample tube containing the sample was weighed to determine a dryweight of the sample.(5) Sodium chloride is dissolved in an aqueous 30 wt % methanol solutionto prepare a saturated saline.(6) 25 mL of the saturated saline obtained in (5) is added to thesample, followed by ion exchange while stirring for 24 hours.(7) Hydrochloric acid produced is titrated using an aqueous 0.02 mol/Lsodium hydrate solution. As an indicator, two drops of a commerciallyavailable phenolphthalein solution for titration (0.1% by volume) areadded and it is judged as the end point when the solution shows areddish purple color.(8) The density of the sulfonic acid group is determined by thefollowing equation.

Density of sulfonic acid group (mmol/g)=[Concentration (mmol/ml) ofaqueous sodium hydroxide solution×amount (ml) added dropwise]/Dry weight(g) of sample

Examples of a method for introducing the ionic group in order to obtainthese ionic group-containing block copolymers to be used for the presentinvention include a method of using a monomer having an ionic group topolymerize it, and a method of introducing an ionic group by a polymerreaction.

In the method of using a monomer having an ionic group to polymerize it,a monomer having an ionic group in a repeating unit may be used. Such amethod is described in, for example. Journal of Membrane Science, 197,2002, p. 231-242. This method can be easily applied to industries andvery preferable since the density of the sulfonic acid group of apolymer can be easily controlled.

A example of the method of introducing an ionic group by a polymerreaction is described as follows. Introduction of a phosphonic acidgroup into an aromatic polymer can be performed by a method describedin, for example. Polymer Preprints, Japan, 51, 2002, p. 750.Introduction of a phosphoric group into an aromatic polymer can beperformed, for example, by phosphate esterifying an aromatic polymerhaving a hydroxyl group. Introduction of a carboxylic acid group into anaromatic polymer can be performed, for example, by oxidizing an aromaticpolymer having an alkyl group or a hydroxyalkyl group. Introduction of asulfate group into an aromatic polymer can be performed, for example, bysulfate esterifying an aromatic polymer having a hydroxyl group. As amethod of sulfonating an aromatic polymer, namely, a method ofintroducing a sulfonic acid group, methods described in, for example,Japanese Unexamined Patent Publication (Kokai) No. 2-16126, and JapaneseUnexamined Patent Publication (Kokai) No. 2-208322 are publicly known.

Specifically, the aromatic polymer can be sulfonated, for example, byreacting the aromatic polymer with a sulfonating agent likechlorosulfonic acid in a solvent such as chloroform, or by reacting thearomatic polymer in concentrated sulfuric acid or fuming, sulfuric acid.The sulfonating agent is not particularly limited as long as it is anagent to sulfonate the aromatic polymer, and sulfur trioxide or the likecan also be used in addition to the above sulfonating agent. When thearomatic polymer is sulfonated by this method, a degree of sulfonationcan be easily controlled by an amount of the sulfonating agent to beused, a reaction temperature and a reaction time. Introduction of asulfonimide group into the aromatic polymer can be performed, forexample, by a method of reacting a sulfonic acid group with asulfonamide group.

Next, a main chain structure of the block (B1) containing an ionic groupto be used in the polymer electrolyte material of the present inventionwill be described specifically.

First, the method for synthesizing an aromatic polyether type polymer tobe used for the present invention is not specifically limited as long asit is a method capable of substantially increasing a molecular weight.For example, the polymer can be synthesized by the aromatic nucleophilicsubstitution reaction of an aromatic active dihalide compound and adiphenolic compound, or the aromatic nucleophilic substitution reactionof a halogenated aromatic phenol compound. The aromatic active dihalidecompound is not specifically limited as long as the molecular weight canbe increased by the aromatic nucleophilic substitution reaction with thediphenolic compound.

It is preferred to use a monomer of a compound obtained by introducingan ionic group into an aromatic active dihalide compound as an aromaticactive dihalide compound to be used for the block (B1) containing anionic group from the viewpoint that the amount of the ionic group can beaccurately controlled. Specific examples of the monomer having asulfonic acid group as the ionic group include, but are not limited to,3,3′-disulfonate-4,4′-dichlorodiphenylsulfone,3,3′-disulfonate-4,4′-difluorodiphenylsulfone,3,3′-disulfonate-4,4′-dichlorodiphenylketone,3,3′-disulfonate-4,4′-difluorodiphenylketone,3,3′-disulfonate-4,4′-dichlorodiphenylphenylphosphine oxide, and3,3′-disulfonate-4,4′-difluorodiphenylphenylphosphine oxide.

From the viewpoint of proton conductivity and resistance to hydrolysis,as the ionic group, a sulfonic acid group is most preferable, but themonomer having an ionic group used for the present invention may haveanother ionic group. Among these monomers,3,3′-disulfonate-4,4′-dichlorodiphenylketone and3,3′-disulfonate-4,4′-difluorodiphenylketone are more preferable in viewof resistance to hot methanol and inhibitory effect of fuel crossover,and 3,3′-disulfonate-4,4′-difluorodiphenylketone is most preferably inview of polymerization activity.

A polymer electrolyte material synthesized by use of3,3′-disulfonate-4,4′-dichlorodiphenylketone and3,3′-disulfonate-4,4′-difluorodiphenylketone as a monomer having anionic group further contains a constituent unit represented by thefollowing general formula (p1) and is preferably employed. This aromaticpolyether-type polymer is more preferably used because it becomes acomponent which is more excellent in resistance to hot methanol than asulfonic acid group in addition to a characteristic of highcrystallinity of a ketone group, and becomes a component useful for amaterial excellent in dimensional stability, mechanical strength andphysical durability at elevated temperature in methanol-water used as afuel. In case of the polymerization, a sulfonic acid group is preferablycombined with a monovalent cation species to form a salt. Examples ofthe monovalent cation species include sodium, potassium or other metalspecies, and various amines cation species, and it is not limited tothese. These aromatic active dihalide compounds can be used alone or incombination.

In the general formula (p1)-, M¹ and M² represent hydrogen, a metalcation, or an ammonium cation, and a1 and a2 represent an integer of 1to 4; and the constituent unit represented by the general formula (p1)may be optionally substituted.

Further, with respect to the aromatic active dihalide compound, it isalso possible to control the density of an ionic group by copolymerizinga compound having an ionic group with a compound not having an ionicgroup. However, it is more preferable for the block (B1) having an ionicgroup of the present invention that an aromatic active dihalide compoundnot having an ionic group is not copolymerized from the viewpoint ofsecuring continuity of a proton conduction path.

Preferred specific examples of the aromatic active dihalide compound nothaving an ionic group include 4,4′-dichlorodiphenylsulfone,4,4′-difluorodiphenylsulfone, 4,4′-dichlorodiphenylketone,4,4′-difluorodiphenylketone, 4,4′-dichlorodiphenylphenylphosphine oxide,4,4′-difluorodiphenylphenylphosphine oxide, 2,6-dichlorobenzonitrile,and 2,6-difluorobenzonitrile. Among these dihalide compounds,4,4′-dichlorodiphenylketone and 4,4′-difluorodiphenylketone are morepreferable from the viewpoint of imparting crystallinity, mechanicalstrength and physical durability, resistance to hot methanol andinhibitory effect of fuel crossover, and 4,4′-difluorodiphenylketone aremost preferable from the viewpoint of a polymerization activity. Thesearomatic active dihalide compounds can be used alone or in combination.

A polymer electrolyte material synthesized by use of4,4′-dichlorodiphenylketone and 4,4′-difluorodiphenylketone as anaromatic active dihalide compound further contains a constituent unitrepresented by the following general formula (p2) and is preferablyemployed. This constituent unit is preferably used because it becomes acomponent to impart an intermolecular cohesive force and crystallinity,and becomes a component useful for a material excellent in dimensionalstability, mechanical strength and physical durability at elevatedtemperature in methanol water used as a fuel and becomes a componentuseful for a material excellent in mechanical strength and durability ina polymer electrolyte fuel cell using hydrogen as a fuel.

the constituent unit represented by the general formula (p2) may beoptionally substituted, but does not contain the ionic group.

Examples of the halogenated aromatic phenol compound is not alsoparticularly limited, and include 4-hydroxy-4′-chlorobenzophenone,4-hydroxy-4r-fluorobenzophenone, 4-hydroxy-4′-chlorodiphenylsulfone,4-hydroxy-4′-fluorodiphenylsulfone, 4-(4′-hydroxybiphenyl)(4-chlorophenyl)sulfone, 4-(4′-hydroxybiphenyl) (4-fluorophenyl)sulfone,4-(4′-hydroxybiphenyl) (4-chlorophenyl)ketone, and4-(4′-hydroxybiphenyl)(4-fluorophenyl)ketone. These halogenated aromaticphenol compounds can be used alone or in combination. In the reaction ofan activated dihalogenated aromatic compound and an aromatic dihydroxycompound, an aromatic polyether-type compound may be synthesized byreacting together with a halogenated aromatic phenol compound.

Examples of the block (B1) containing an ionic group ▪ to be used forthe present invention is particularly preferably an aromaticpolyetherketone-type copolymer comprising constituent units representedby the following general formulas (P1) and (P2) containing constituentunits represented by the above general formulas (p1) and (p2):

In the general formulas (P1) and (P2), A represents a divalent organicgroup containing an aromatic ring and M1 and M2 represent hydrogen, ametal cation, or an ammonium cation; and “A” in formula P2 may representtwo or more kinds of groups.

By changing the composition ratio of constituent units represented bythe general formulas (PI) and (P2), it is possible to control thedensity of a sulfonic acid group, but an amount of PI to be introducedbased on a total molar amount of PI and P2 is preferably 50 mol % ormore, more preferably 75 mol % or more, and most preferably 90 mol % ormore. When the amount of PI to be introduced is less than 50 mol %,construction of a proton conduction path becomes inadequate and it isnot preferable.

Herein, as the divalent organic group A containing an aromatic ring inthe general formulas (PI) and (P2), various diphenolic compounds, whichcan be used for polymerization of an aromatic polyether-type polymer bythe aromatic nucleophilic substitution reaction, can be employed, and itis not particularly limited. It is also possible to use a compoundobtained by introducing a sulfonic acid group into these aromaticdihydroxy compounds as a monomer.

Preferable specific examples of the divalent organic group A containingan aromatic ring include groups represented by the following generalformulas (X-1) to (X-29):

Wherein the group represented by the formulas (X-1) to (X-7) may beoptionally substituted.

Wherein n and m represent an integer of 1 or more, and Rp represents anoptional organic group.

These may have a substituent and′ an ionic group. A divalent organicgroup A having an aromatic ring in the side chain is also preferableexample. These can be used in combination, if necessary.

Among these groups, from the viewpoint of crystallinity, dimensionalstability and mechanical strength, groups represented by the generalformulas (X-1) to (X-7) are more preferable, groups represented by thegeneral formulas (X-1) to (X-5) are furthermore preferable, and a grouprepresented by the general formula (X-2) or (X-3) is most preferable.

The polymer electrolyte material of the present invention is suitablyused for the polymer electrolyte form article. In the present invention,the polymer electrolyte form article means a form article containing thepolymer electrolyte material of the present invention.

The polymer electrolyte form article in the present invention can takevarious forms such as membrane (including film and film-shaped article),plate-like, fiber-like, hollow fiber-like, particle-like, bulk-like,microporous-like, coatings, foams and the like according to thepurposes. It can be adapted to wide use because it can improve designflexibility of a polymer and various characteristics such as mechanicalproperties and resistance to a solvent. Particularly, the polymerelectrolyte form article is preferable in a membrane form.

When the polymer electrolyte material of the present invention is usedas fuel cell, the material is preferably used for the polymerelectrolyte membrane and the electrocatalyst layer. Particularly, thematerial is preferably used for the polymer electrolyte membrane. Thereason for this is that in case of using the material as fuel cell, thematerial is usually used as the polymer electrolyte membrane or a binderof the electrocatalyst layer in a membrane state.

The polymer electrolyte membrane of the present invention can be appliedto various purposes. For example, the polymer electrolyte membrane canbe applied to medical purposes such as extracorporeal circulation columnand artificial skin, purposes for filtration, purposes for ion exchangeresin such as chlorine-tolerant reverse osmosis membrane, purposes forvarious structural materials, electrochemical purposes, humidifyingmembranes, antifogging membranes, antistatic membranes, membranes forsolar cell, and gas barrier materials. Moreover, the polymer electrolytemembrane is suited for artificial muscle and actuator materials. Amongthese purposes, the polymer electrolyte material or the polymerelectrolyte form article can be more preferably used for variouselectrochemical purposes. The electrochemical purposes include, forexample, a fuel cell, a redox flow cell, a water electrolysis apparatus,and a chloroalkali electrolysis apparatus. Among these purposes, a fuelcell is most preferable.

Next, a production method for obtaining the polymer electrolyte formarticle of the present invention is described as follows.

Conventional ionic group-containing block copolymers were all amorphouspolymers because they have a bulky ionic group such as a sulfonic acidgroup and due to the synthetic constraint that solubility in a solventis required in polymerization or in forming a membrane. Since theseamorphous ionic group-containing block copolymer is low in a cohesiveforce of a polymer chain, they are deficient in toughness or stabilityof a polymer higher-order structure and could not achieve sufficientmechanical strength and physical durability when being formed into theform of membrane. Further, since a thermal decomposition temperature ofthe ionic group is lower than a melting point, melt processing isdifficult and solution casting method is usually employed, and thereforean uniform and tough membrane could not be obtained in a polymercontaining a crystal insoluble in a solvent.

The polymer electrolyte form article of the present invention is apolymer electrolyte material composed of an ionic group-containing blockcopolymer having a block (B1) containing an ionic group and a block (B2)substantially not containing an ionic group, in which a ratio W1/W2 ofweight W1 of the B1 to weight W2 of the B2 is 0.2 or more and 5 or less,and it is obtained by forming a polymer electrolyte material in whichprotecting groups are introduced into at least a block (B2), and thendeprotecting at least a portion of the protective groups contained inthe form article.

When the block (B2) substantially not containing an ionic group iscrystalline, since processability tends to become poor due tocrystallization of a polymer by domain formation compare with the casewhere a random copolymer is used, it is preferred to improve theprocessability by introducing protective groups into at least the block(B2). Also with respect to the block (B1) containing an ionic group, itis preferred to introduce protective groups when the processabilitybecomes poor.

Specific examples of the protective group to be used for the presentinvention include a protective group used commonly in organic synthesis,and the protective group is a substituent temporarily introduced on theassumption that it is removed in the following stages, which protects afunctional group having high reactivity and makes the functional groupinert for a subsequent reaction, and can deprotect the functional groupafter the reaction to return to an original functional group. That is,the protective group is a group paired with″ a functional group to beprotected, and examples thereof include the case where a t-butyl groupis used as a protective group of a hydroxyl group, but the case where at-butyl group is introduced into an alkylene chain is not referred to asa protective group. The reaction for introducing a protective group isreferred to as a protection (reaction), while the reaction for removinga protective group is referred to as a deprotection (reaction).

Such a protection reaction is described in detail, for example, inTheodora W. Greene, “Protective Groups in Organic Synthesis”, U.S.A.,John Wiley & Sons, Inc, 1981, and the protection reaction can bepreferably used. The protective group can be appropriately selectedtaking account of reactivity and yield of the protection reaction anddeprotection reaction, stability of protective group-containing state,and production cost. The stage, at which the protective group isintroduced in the polymerization reaction, may be a monomer, an oligomeror a polymer, and can be appropriately selected.

Specific examples of the protection reaction include a method forprotecting/deprotecting a ketone group with a ketal group, and a methodfor protecting/deprotecting a ketone group with a heteroatom analog of aketone group, for example, thioketal. These methods are described inChapter 4 of aforementioned “Protective Groups in Organic Synthesis”.Examples thereof further include a method for protection/deprotectionbetween sulfonic acid and a soluble ester derivative, and a protectionmethod of introducing a t-butyl group into an aromatic ring and adeprotection method through de-t-butylation with an acid. However, theprotection/deprotection is not limited to these, and anyprotection/deprotection can be preferably used as long as a group is aprotective group. In view of improving solubility of the polymer in acommon solvent, it is preferred to use, as the protective group, analiphatic group having large steric hindrance, particularly an aliphaticgroup containing a cyclic moiety.

The position of the functional group, at which the protective group isintroduced, is preferably a main chain of the polymer. In the polymerelectrolyte material of the present invention, since the protectivegroup is introduced into a polymer having good packing for the purposeof improving processability, sometimes an adequate effect of the presentinvention cannot be achieved even though the protective groups areintroduced into the side chain of the polymer. As used herein, thefunctional group, which is present in the main chain of the polymer, isdefined as a functional group in which a polymer chain is cleaved whenthe functional group is eliminated. For example, this means that if aketone group of aromatic polyetherketone is eliminated, benzene ringsare isolated from one another.

More preferable protection reaction are a method forprotecting/deprotecting a ketone group with a ketal group, and a methodfor protecting/deprotecting a ketone group with a heteroatom analog of aketone group, for example, thioketal in view of reactivity andstability. In the polymer electrolyte material and the polymerelectrolyte membrane the present invention, a constituent unitcontaining a protective group is more preferably a constituent unitcontaining at least one selected from the following general formulas(P3) and (P4).

In the formulas (P3) and (P4), Ar₁ to Ar₄ represent an optional divalentarylene group, R₁ and R₂ represent a least one group selected from H andan alkyl group, R₃ represents an optional alkylene group, E represents 0or S, and each group may represent two or more kinds of groups; andgroups represented by the formulas (P3) and (P4) may be optionallysubstituted.

Particularly, E is O in the above general formulas (P3) and (P4) in viewof smell, reactivity and stability of a compound, that is, a method forprotecting/deprotecting a ketone group with a ketal group is mostpreferable.

R₁ and R₂ in the general formula (P3) are more preferably an alkyl groupin view of stability, furthermore preferably an alkyl group having 1 to6 carbon atoms, and most preferably an alkyl group having 1 to 3 carbonatoms. Further, R₃ in the general formula (P4) is more preferably analkylene group having 1 to 7 carbon atoms in view of stability, and mostpreferably an alkylene group having 1 to 4 carbon atoms. Specificexamples of R₃ include, but are not limited to, —CH₂CH₂—, —CH(CH₃)CH₂—,—CH(CH₃)CH(CH₃)—, —C(CH₃)2CH₂—, -c(CH₃)₂CH(CH₃)—C(CH₃)0(CH₃)₂ _(_),—CH₂CH₂CH₂—, and —CH₂C(CH₃)2CH₂—.

The constituent unit having at least the general formula (P4) of theabove constituent unit having the general formula (P3) or (P4) ispreferably used from the viewpoint of stability such as resistance tohydrolysis. Furthermore, R3 in the general formula (P4) is preferably analkylene group having 1 to 7 carbon atoms, that is, a group representedby Cn1H2n1 (n1 is an integer of 1 to 7), and most preferably at leastone selected from —CH₂CH₂—, —CH(CH₃)CH₂—, or —CH₂CH₂CH₂— in view ofstability and ease of synthesis.

An organic group as Ar₁ to Ar₄ in the general formulas (P3) and (P4) ispreferably a phenylene group, a naphthylene group, or a biphenyl group.These organic groups may be optionally substituted. As the aromaticpolyether-type polymer of the present invention, in view of solubilityand ease of availability, both Ar₃ and Ar₄ in the above general formula(P4) are more preferably a phenylene group, and both Ar₃ and Ar₄ aremost preferably a p-phenylene group.

In the present invention, the method of protecting a ketone group withketal includes a method of reacting a precursor compound having a ketonegroup with a monofunctional and/or difunctional alcohol in the presenceof an acid catalyst. For example, it can be produced by reacting4,4′-dihydroxybenzophenone which is a ketone precursor withmonofunctional and/or difunctional alcohol in the presence of an acidcatalyst such as hydrogen bromide in a solvent such as aliphatic oraromatic hydrocarbons. The alcohol is aliphatic alcohol having 1 to 20carbon atoms. An improved method for producing a ketal monomer to beused for the present invention comprises reacting4,4̂-dihydroxybenzophenone which is a ketone precursor with difunctionalalcohol in the presence of alkyl ortho ester and a solid catalyst.

In the present invention, a method in which at least a part of a ketonegroup protected with ketal is deprotected to form a ketone group is notparticularly limited. The above deprotection reaction can be performedin the presence of water and acid under a nonuniform or uniformcondition, but a method, in which an acid treatment is performed afterforming a membrane, is more preferable from the viewpoint of mechanicalstrength, physical durability and resistance to solvents. Specifically,the formed membrane can be deprotected by immersing it in a hydrochloricacid aqueous solution or a sulfuric acid aqueous solution, and aconcentration of acid or a temperature of the aqueous solution can beappropriately selected.

A weight ratio of the required acid aqueous solution to the polymer ispreferably 1 to 100 times, but a larger amount of water can also beused. An acid catalyst is preferably used in a concentration of 0.1 to50% by weight of water being present. Examples of preferable acidcatalyst include a strong mineral acid such as hydrochloric acid, nitricacid, fluorosulfonic acid, or sulfuric acid, and a strong organic acidsuch as p-toluenesulfonic acid or trifluoromethanesulfonic acid.According to the membrane thickness of a polymer, the acid catalyst, anamount of excess water and a reaction pressure can be appropriatelyselected.

In case of a membrane having a thickness of 50 μm, it is possible todeprotect almost all of protective groups by immersing the membrane inan aqueous 6N hydrochloric acid solution and heating at 95° C. for 1 to48 hours. It is also possible to deprotect almost all of protectivegroups by immersing the membrane in an aqueous 1N hydrochloric acidsolution at 25° C. for 24 hours. However, the conditions of deprotectionare not limited to these conditions and it is possible to deprotect withan acidic gas or an organic acid, or a heat treatment.

Also when the aromatic polyether-type polymer includes a bond form suchas a direct bond other than an ether bond, a position of the protectivegroup introduced is more preferably a portion of the aromatic ether-typepolymer from the viewpoint of improving processability.

Specifically, the aromatic polyether-type polymer comprising constituentunit represented by the general formula (P3) or (P4) can be synthesizedby using, as a diphenolic compound, a compound represented by thefollowing general formulas (P3-1) and (P4-1), followed by the aromaticnucleophilic substitution reaction of the compound with an aromaticactive dihalide compound. The constituent units represented by thegeneral formulas (P3) and (P4) may be derived from either the diphenoliccompound or the aromatic active dihalide compound, but are morepreferably derived from the diphenolic compound taking account ofreactivity of the monomer.

In the general formulas (P3-1) and (P4-1), Ar₁ to Ar₄ represent anoptional divalent arylene group, R₁ and R₂ represent at least one kindof a group selected from H and an alkyl group, R₃ represents an optionalalkylene group, and E represents O or S; and the groups represented bythe general formulas (P3-1) and (P4-1) may be optionally substituted.

Specific examples of particularly preferable—diphenolic compound to beused for the present invention include compounds represented by thefollowing general formulas (r1) to (r10), and derivatives derived fromthese diphenolic compounds.

Among these diphenolic compounds, compounds represented by the generalformulas (r4) to (r10) are more preferable in view of stability, morepreferably compounds represented by the general formulas (r4), (r5) and(r9), and most preferably a compound represented by the general formula(r4).

In the polymer electrolyte membrane of the present invention, the protonconductivity per unit area and per unit thickness is preferably 10 mS/cmor more, more preferably 20 mS/cm, and still more preferably 50 mS/cm ormore. A sample of a membrane was immersed in pure water at 25° C. for 24and taken out in an atmosphere at 25° C. and a relative humidity of 50to 80%, and then proton conductivity was measured as quick as possibleusing a potentiostatic AC impedance method.

When proton conductivity per unit area and per unit thickness is 10mS/cm or more, sufficient proton conductivity, namely, sufficient cellpower can be obtained when the membrane is used as a polymer electrolytemembrane for fuel cell. The higher proton conductivity, the better.However, when proton conductivity is too high, the membrane having highproton conductivity is likely to be dissolved or collapsed by the fuelsuch as methanol water and also fuel crossover may increase. Therefore,actual upper limit is 5,000 mS/cm.

In the polymer electrolyte membrane of the present invention, methanolcrossover per unit area and per unit thickness with respect to anaqueous 1 mol % methanol solution under the condition of 20° C. is 100nmol/min/cm or less. Methanol crossover is more preferably 50nmol/min/cm or less, and still more preferably 10 nm/min/cm or less. Thereason is as follows. That is, in the fuel using the membrane of thepolymer electrolyte material, it is desired that fuel crossover is smallso as to maintain high concentration of the fuel in view of obtaininghigh power and high energy capacity in the region of high concentrationof the fuel. On the other hand, in view of ensuring proton conductivity,fuel crossover is more preferably 0.01 nmol/min/cm or more.

The proton conductivity per unit area, measured under the aboveconditions, is preferably 3 S/cm² or more, more preferably 5 S/cm² ormore, and furthermore preferably 7 S/cm² or more. By adjusting protonconductivity per unit area to 3 S/cm² or more, a high-power fuel cellcan be obtained. On the other hand, since the membrane having highproton conductivity is likely to be dissolved or collapsed by the fuelsuch as methanol water and its fuel crossover tends to increase.Therefore, actual upper limit of the proton conductivity is 500 S/cm².

In the polymer electrolyte membrane of the present invention, methanolcrossover per unit area with respect to an aqueous 1 mol % methanolsolution under the condition of 20° C. is preferably 5 μmol/min/cm² orless. The reason is as follows. That is, in the fuel using the membraneof the polymer electrolyte material, it is desired the fuel crossover issmall so as to maintain high concentration of the fuel in view ofobtaining high power and high energy capacity in the region of highconcentration of the fuel. From such a view point, it is more preferablethat the methanol crossover is 2 μmol/min/cm² or less, and mostpreferable 1 μmol/min/cm² or less. From the view point of ensuring theproton conductivity, 0.01 μmol/min/cm² or more is preferable.

The polymer electrolyte material of the present invention, in case ofusing it in DMFC, preferably achieves low methanol crossover and highproton conductivity as described above at the same time. The reason forthis is that to achieve one of low methanol crossover and high protonconductivity is easy even in the prior art, but compatibility betweenhigh power and high energy capacity becomes possible by achieving bothlow methanol crossover and high proton conductivity.

In the polymer electrolyte material and the polymer electrolyte membraneof the present invention, in view of fuel barrier properties and anincrease of energy capacity using a high concentration fuel, it is morepreferable that the polymer electrolyte material is excellent inresistance to solvents, that is, weight loss of the polymer electrolytematerial after immersing in N-methyl pyrrolidone at 100° C. for 2 hoursis 70% by weight or less. As the liquid fuel, alcohols such as methanolare often used. In the present invention, resistance to solvents isevaluated using N-methyl pyrrolidone having excellent solubilityregardless of the kind of the polymer. Weight loss is more preferably50% by weight or less, and most preferably 30% by weight or less. Weightloss of more than 70% by weight is not preferred because mechanicalstrength and physical durability are insufficient because ofinsufficient fuel barrier properties and insufficient crystallinity. Incase of using for DMFC in which an aqueous high-temperature andhigh-concentration methanol solution is used as the fuel, the membranesolves or swells drastically. Moreover, it becomes difficult to directlyapply a catalyst paste on the polymer electrolyte membrane to produce amembrane electrode assembly, and thus not only production cost increasesbut also interface resistance with the catalyst layer increases andsufficient power generation characteristics may not be obtained.

In the present invention, to be excellent in resistance to hot water andresistance to hot methanol means that changes in dimensions (swelling)in hot water and hot methanol, respectively, are small. When thisdimensional change is large, it is not preferable because the membranebreaks or the membrane is peeled off from an electrocatalyst layer dueto swelling to cause an increase in resistivity during using as apolymer electrolyte membrane. Further, when it is inferior in resistanceto hot water and resistance to hot methanol, it is not preferablebecause in case of using a high concentration fuel such as a highconcentration methanol aqueous solution, the polymer electrolytemembrane or a binder of a catalyst layer is dissolved in the fuel. Thesecharacteristics of resistance to hot water and resistance to hotmethanol are both important characteristics required to an electrolytepolymer used in a polymer electrolyte fuel cell.

In the polymerization by the aromatic nucleophilic substitutionreaction, which is carried out in order to obtain an aromaticpolyether-type polymer to be used in the present invention, a polymercan be obtained by reacting a mixture of the above monomers in thepresence of a basic compound. The polymerization can-be carried out at atemperature within a range from 0 to 350° C., but the temperature ispreferably 50 to 250° C. When the temperature is lower than 0° C., thereaction may not tend to proceed adequately, and when the temperature ishigher than 350° C., decomposition of the polymer may tend to beinitiated. The reaction can be carried out in the absence of a solvent,but is preferably carried out in a solvent. Examples of usable solventinclude aprotic polar solvents such as N,N-dimethylacetamide,N,N-dimethylformamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide,sulfolane, 1,3-dimethyl-2-imidazolidinone, andhexamethylphosphonetriamide, but the usable solvent is not limited tothese solvent and may be any solvent which can be used as a stablesolvent in the aromatic nucleophilic substitution reaction. Theseorganic solvents can be used alone or in combination.

Examples of the basic compound include sodium hydroxide, potassiumhydroxide, sodium carbonate, potassium carbonate, sodium hydrogencarbonate, and potassium hydrogen carbonate, but the basic compound canbe used without being limited to these compounds as long as it canconvert aromatic diols into an active phenoxide structure.

In the aromatic nucleophilic substitution reaction, water is sometimesproduced as by-product. In this case, water can also be removed out ofthe system in the form of an azeotrope by making toluene or the likecoexist irrespective of a polymerization catalyst in the reactionsystem. As the method of removing water out of the system, an absorbentsuch as molecular sieve can be used.

An azeotropic agent used for removing reaction water or water introducedduring the reaction is generally any inert compound which does notsubstantially interfere with polymerization, is azeotropically distilledwith water and boiled at a temperature of about 25 to about 250° C.Common azeotropic agent is such as benzene, toluene, xylene,chlorobenzene, methylene chloride, dichlorobenzene, andtrichlorobenzene. Naturally, it is useful to select such azeotropicagent that its boiling point is lower than that of a dipolar solventused. Generally, the azeotropic agent is used, but it is not alwaysnecessary when a high reaction temperature, for example, a temperatureof 200° C. or higher, is employed, particularly when an inert gas iscontinuously flowed over a reaction mixture. Generally, the reaction isdesirably performed in a state of oxygen-free in an inert atmosphere.

When the aromatic nucleophilic substitution reaction is carried out in asolvent, the monomer is preferably charged so as to adjust theconcentration of the resulting polymer within a range from 5 to 50% byweight. When the concentration is less than 5% by weight, thepolymerization degree may hardly increase. On the other hand, when theconcentration is more than 50% by weight, viscosity of the reactionsystem increases and it may become difficult to subject the reactionproduct to a post-treatment.

After the completion of the polymerization reaction, the reactionsolution is vaporized to remove the solvent and the residual substanceis optionally washed to obtain a desired polymer. Also, the reactionsolution is poured into a solvent having low solubility with a polymerand high solubility with an inorganic salt produced as by-product,thereby to remove the inorganic salt and to precipitate a polymer as asolid, and the precipitate is collected by filtration to obtain apolymer. The recovered polymer is optionally washed with water, analcohol or other solvents, and then dried. When a desired molecularweight is obtained, a halide end group or a phenoxide end group can beoptionally reacted by introducing a phenoxide or a halide end groupsealing agent to produce a stable end group.

A molecular weight of the ionic group-containing polymer of the presentinvention thus obtained is 1000 to 5000000, and preferably 10000 to500000 in terms of a polystyrene equivalent weight average molecularweight. When the molecular weight is less than 1000, cracks may beproduced in the formed membrane and either of mechanical strength,physical durability and resistance to solvents may be insufficient. Onthe other hand, when the molecular weight is more than 500000, there areproblems that solubility becomes inadequate, viscosity of a solution ishigh and processability becomes poor.

In addition, a chemical structure of the polymer electrolyte material ofthe present invention can be identified by S═O absorption at 1,030 to1,045 cm⁻¹ and 1,160 to 1,190 cm⁻¹, C—O—C absorption at 1,130 to 1,250cm⁻¹ and C═O absorption at 1,640 to 1,660 cm⁻¹ through infraredabsorption spectrum, and the composition ratio thereof can be determinedby acid-base titration or elemental analysis of sulfonic acid groups.Also, the structure can be confirmed by a peak of an aromatic proton at6.8 to 8.0 ppm through a nuclear magnetic resonance spectrum (¹H-NMR).Also, the position and arrangement of a sulfonic acid group can beconfirmed through solution ¹³C-NMR and solid-state ¹³C-NMR.

Next, a specific method of the ionic group-containing block copolymercomprising a block (B1) containing an ionic group and a block (B2)substantially not containing an ionic group is exemplified. However, thepresent invention is not limited these.

Examples of the ionic group-containing block copolymer to be used forthe present invention include a block copolymer formed by reacting anionic group-containing monomer and a monomer not containing an ionicgroup separately to form an ionic group-containing block represented bythe following formula (H3-2), and/or a block not containing an ionicgroup represented by the following formula (H3-1), and then randomcopolymerizing these blocks. Further, examples of the ionicgroup-containing block copolymer include a block copolymer formed byreacting an ionic group-containing monomer and a polymer not containingan ionic group represented by the following formula (H3-1), a blockcopolymer formed by reacting a monomer not containing an ionic group andan ionic group-containing polymer represented by the following formula(H3-2), and a block copolymer by spontaneously forming a block from onlya monomer taking advantage of the difference in reactivity betweenmonomers. Furthermore, it is also possible that after obtaining a blockcopolymer having aromatic rings with different reactivities of asulfonation reaction, namely, with different electron densities, anionic group is selectively introduced into only a highly reactive site.

However, in the above method of forming an ionic group-containing blockrepresented by the following formula (H3-2), and/or a block notcontaining an ionic group represented by the following formula (H3-1),and then random copolymerizing these blocks, control of a block lengthwas difficult since the reactivity of the ionic group-containing blockis significantly different from that of the block not containing anionic group because of steric hindrance.

Accordingly, in the present invention, a method of forming an ionicgroup-containing block represented by the following formula (H3-4),and/or a block not containing, an ionic group represented by thefollowing formula (H3-3), and then cross-copolymerizing these blocks canbe more preferably used. According to the above description, it becomespossible to synthesize a block copolymer having a required block length.

Here, in the following formulas (H3-3) and (H3-4), an ionicgroup-containing block of F terminal and a block not containing an ionicgroup of OK terminal are shown, but these may be reversed.

In the above formulas (H3-1) to (H3-4), a halogen atom is represented byF, and an alkaline metal is represented by Na and K, but they are notlimited to these and others can be used. The above formulas are insertedfor the purpose of helping the understanding of readers, and do notalways express precisely a chemical structure, exact composition,arrangement, a position of a sulfonic acid, quantity and a molecularweight of polymerizing components, of a polymer, and the presentinvention is not limited to these chemical structural formulas.

Furthermore, in the aforementioned formulas (H3-1) to (H3-4), a ketalgroup is introduced into any block as a protective group. However, inthe present invention, the protective group may be introduced into acomponent having high crystallinity and low solubility and theaforementioned formulas (H3-2) and (H3-4) do not necessarily require theprotective group, and it is preferable that there is no the protectivegroup from the viewpoint of durability and dimensional stability.

Further, with respect to a block shown in the formula (H3-3), anoligomer with a controlled molecular weight can be synthesized byreacting a bisphenol component and an aromatic dihalide component inproportions of N₃: (N₃+1). The same holds true with regard to theformula (H3-4).

The method of forming the polymer electrolyte material of the presentinvention into a polymer electrolyte membrane is not particularlylimited, and a method of forming a membrane from a solution state or amethod of forming a membrane from a molten state can be used in a stageof having a protective group such as ketal. In the former, for example,the polymer electrolyte material is dissolved in a solvent such asN-methyl-2-pyrrolidone and the solution is applied and spread over aglass plate, and then the solvent is removed to form a membrane.

As the solvent be used to form a membrane, any can be used as long as apolymer electrolyte material can be dissolved in it and it can beremoved, and an aprotic polar solvent such as N,N-dimethylacetamide,N,N-dimethylformamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide,sulfolane, 1,3-dimethyl-2-imidazolidinone, andhexamethylphosphonetriamide; an ester-type solvent such asy-butyrolactone or butyl acetate; a carbonate-type solvent such asethylene carbonate or propylene carbonate; an alkylene glycol monoalkylether such as ethylene glycol monomethyl ether, ethylene glycolmonoethyl ether, propylene glycol monomethyl ether, and propylene glycolmonoethyl ether; an alcohol-type solvent such as isopropanol; water anda mixture thereof are preferably used, and an aprotic polar. solvent ispreferable because of its high solubility.

Further, in the present invention, when the block copolymer is used,selection of the solvent is important for a phase separation structure,and a method of mixing an aprotic polar solvent and a less polar solventto use is preferable.

It is preferred to subject a polymer solution prepared so as to have arequired solid content to filtration under pressured or not to removeimpurities (or unknown substances) contained in the polymer electrolytesolution, in order to obtain a tough membrane. A filter medium usedherein is not specifically limited and is preferably a glass filter or ametal filter. A minimum pore size of the filter, through which thepolymer solution passes in the filtration, is preferably 1 pm or less.If the polymer is not subjected to filtration, it is not preferablesince it allows impurities matters to mix in to cause break of amembrane or deterioration of durability.

Then, in the resulting polymer electrolyte membrane, it is preferred toheat treatment at least a part of the ionic group in a state of metalsalt. If the polymer electrolyte material to be used is a polymer whichis polymerized in a state of metal salt in polymerization, it ispreferably formed into a membrane and heat treated as it is. Metals inmetal salts may be those capable of forming salts with sulfonic acid,but it is preferably Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Ti, V, Mn, Fe,Co, Ni, Cu, Zn, Zr, Mo, and W, and among these metals, Li, Na, K, Ca,Sr, and Ba are more preferable, and Li, Na, K are furthermorepreferable.

The temperature of the heat treatment is preferably from 150 to 550° C.,more preferably from 160 to 400° C., and particularly preferably from180 to 350° C. The time for heat treatment is preferably from 10 secondsto 12 hours, more preferably from 30 seconds to 6 hours, andparticularly preferably from one minute to one hour. When thetemperature of the heat treatment is too low, an effect of inhibitingfuel crossover, elastic modulus and strength at break are insufficient.On the other hand, when the temperature of the heat treatment is toohigh, a membrane material tends to deteriorate. When a time of a heattreatment is less than 10 seconds, an effect of heat treatment isdeficient. On the other hand, when the time of a heat treatment is morethan 12 hours, a membrane material tends to deteriorate. The polymerelectrolyte membrane obtained by the heat treatment is capable of protonsubstitution by immersing it in an acid aqueous solution as required.Forming by this method enables the polymer electrolyte membrane of thepresent invention it to achieve proton conductivity and fuel barrierproperties simultaneously in a good balance.

As a method for converting the polymer electrolyte material used in thepresent invention to a membrane, there is a method in which a membranecomposed of the polymer electrolyte material is prepared by the abovetechnique, and then at least a part of a ketone group protected withketal is deprotected to form a ketone group. In accordance with thismethod, it becomes possible to form a membrane from a solution of ablock copolymer with low solubility comprising a block not containing anionic group, and it becomes possible to achieve proton conductivity andfuel barrier properties simultaneously, and excellent resistance tosolvents, mechanical strength and physical durability.

In the polymer electrolyte membrane of the present invention, thepolymer structure can be furthermore optionally crosslinked by meanssuch as irradiation. By crosslinking such polymer electrolyte membrane,it is possible to expect an effect of further inhibiting fuel crossoverand swelling due to fuel, and mechanical strength may be improved andthe electrolyte membrane may become better. Irradiation includes, forexample, irradiation with electron beam and irradiation with y-ray.

With respect to a membrane thickness of the polymer electrolyte membraneof the present invention, a membrane having a thickness of 1 to 2,000 μmis preferably used. For the purpose of obtaining the mechanical strengthand the physical durability of a membrane enduring practical use, thethickness is more preferably more than 1 pm, and for the purpose ofdecreasing membrane resistance, namely, improving of power generationperformance, the thickness is preferably less than 2000 μm. Thethickness is more preferably from 3 to 500 μm, and particularlypreferably from 5 to 250 μm. The thickness can be controlled by theconcentration of the solution or the thickness of the coat on asubstrate.

Moreover, additives used in a conventional polymer compound, forexample, crystallization nucleating agents, plasticizers, stabilizers,antioxidants and releasants can be added to the polymer electrolytemembrane as long as the object of the present invention is not adverselyaffected.

Further, as long as various properties described above are-not adverselyaffected, the polymer electrolyte membrane obtained according to thepresent invention can contain various polymers, elastomers, fillers,fine particles and various additives for the purpose of improvingmechanical strength, thermal stability and processability. Moreover, themembrane may be reinforced with a fine porous membrane, a nonwovenfabric or a mesh.

Further, a membrane electrode assembly obtained according to the presentinvention means a membrane electrode assembly containing the polymerelectrolyte membrane of the present invention or the polymer electrolytematerial of the present invention in a polymer electrolyte membrane orin a catalyst layer. The membrane electrode assemblies are parts inwhich the polymer electrolyte membrane and an electrode are assembled.

The method for assembling a polymer electrolyte membrane with anelectrode when the polymer electrode membrane is used for fuel cell isnot specifically limited, and well-known methods (for example, chemicalplating method described in Electrochemistry, 1985, 53, p. 269, andthermal press-bonding method by a gas diffusion electrode, described inElectrochemical Science and Technology, edited by J. Electrochem. Soc.,1988, 135, 9, p. 2209) are applicable thereto.

In case of assembling using a hot press, the temperature and thepressure are appropriately selected according to the thickness of theelectrolyte membrane, the moisture content, the catalyst layer or theelectrode substrate. Moreover, in the present invention, assembling canbe carried out by press even if the electrolyte membrane is dried or themembrane is water-absorbed. Specific examples of the press methodincludes roll press in which the pressure and the clearance are defined,and flat plate press in which the pressure is defined, and the press ispreferably carried out at a temperature within a range of 0 to 250° C.from the viewpoint of industrial productivity and inhibition of thermaldecomposition of the polymer electrolyte material having an ionic group.It is preferable that the pressure is as low as possible from theviewpoint of protection of the polymer electrolyte membrane and theelectrode, and in the case of the flat plate press, the pressure ispreferably 10 MPa or less, and it is one of preferable′ choices from theviewpoint of prevention of short-circuit of anode and cathode tolaminate an electrode and a polymer electrolyte membrane to manufacturea fuel cell without assembling by a hot press process. In case of thismethod, when power generation is repeated as the fuel cell,deterioration of the polymer electrolyte membrane, which is consideredto be caused by the short-circuited portion, may be inhibited anddurability as a fuel cell is improved.

The fuel of the fuel cell using the membrane electrode assembly of thepresent invention includes oxygen, hydrogen, an organic compound having1 to 6 carbon atoms such as methane, ethane, propane, butane, methanol,isopropyl alcohol, acetone, glycerin, ethylene glycol, formic acid,acetic acid, dimethyl ether, hydroquinone, or cyclohexane, and a mixtureof water of the compound, and these fuels may be used alone or incombination. Particularly, from the viewpoint of power generationefficiency and the system simplification of the entire cell, hydrogenand a fuel containing an organic compound having 1 to 6 carbon atoms arepreferably used, and in view of power generation efficiency, hydrogenand an aqueous methanol solution are particularly preferably used. Incase of using an aqueous methanol solution, the concentration ofmethanol is appropriately selected according to the system of the fuelcell to be used. However, the concentration is preferably as high aspossible from the viewpoint of long-term, operation. For example, in theactive-type fuel cell having auxiliary machines such as a system ofsupplying a medium required for power generation to the membraneelectrode assembly, for example, a liquid supply pump and a blower fan,a cooling fan, a fuel diluting system and a product recovery system, itis preferable that the fuel having the methanol concentration of 30 to100% or more is injected from a fuel tank or a fuel cassette, diluted toabout 0.5 to 20% and then supplied to the membrane electrode assembly. Afuel having a methanol concentration of 10 to 100% is preferable for apassive-type fuel cell having no auxiliary machine.

Furthermore, applications of a polymer electrolyte fuel cell using thepolymer electrolyte membrane of the present invention, but notparticularly limited, are preferably electric power supply for mobileobjects. Particularly, it is preferably used as electric power supplyfor portable devices such as cellular phone, personal computer, PDA,television set, radio, music player, game machine, headset and DVDplayer, various robots such as industrial humanoid robot and animal typerobot, household appliances such as cordless cleaners, toys, and mobilebodies, for example, vehicles such as electric bicycle, motorcycle,automobile, bus and trucks, marine vessels and railroads; substitutionsof conventional primary and secondary cells, such as stationary typepower generator; or hybrid power sources in which this polymerelectrolyte fuel cell is used in combination with conventional primaryand secondary cells.

EXAMPLES

The present invention will now be described by way of examples, but thepresent invention is not limited to the following examples. Measuringconditions of the respective physical properties are as follows.Further, chemical structural formulas are inserted in the presentExamples, but these chemical structural formulas are inserted for thepurpose of helping the understanding of readers, and do not alwaysexpress precisely a chemical structure, exact composition, arrangement,a position of a sulfonic acid and a molecular weight of polymerizingcomponents of a polymer, and the present invention is not limited tothese chemical structural formulas.

(1) Density of Sulfonic Acid Group

A sample of a membrane as a specimen was immersed in pure water at 25°C. for 24 hours and, after vacuum drying at 40° C. for 24 hours,elemental analysis was carried out. Analysis of carbon, hydrogen andnitrogen was carried out by a full automatic elemental analysisapparatus varioEL, analysis of sulfur was carried out by flaskcombustion method and titration with barium acetate, and analysis offluorine was carried out by flask combustion and ion chromatogrammethods. Density (mmol/g) of sulfonic acid group per unit gram wascalculated from a composition ratio of a polymer.

(2) Proton Conductivity

After a sample of a membrane was immersed in pure water at 25° C. for 24hours, it was held in a thermo-hygrostat of 80° C. and a relativehumidity of 95% for 30 minutes, and then proton conductivity wasmeasured by a potentiostatic AC impedance method.

As a measuring apparatus, an electrochemical measuring systemmanufactured by Solartron (Solartron 1287 Electrochemical Interface andSolartron 1255B Frequency Response Analyzer) was used, and apotentiostatic impedance was measured by a two-terminal method todetermine proton conductivity. An AC amplitude was set at 50 mV. As asample, a membrane of 10 mm in width and 50 mm in length was used. Ameasuring jig was made of a phenolic resin and a measuring section wasopened. Platinum plates (two plates of 100 pm in thickness) were used asan electrode. The electrodes were located at a distance of 15 mm ontopside and reverse side of a sample membrane-so as to be parallel toeach other and orthogonal to a longitudinal direction of the samplemembrane.

(3) Number Average Molecular Weight, Weight Average Molecular Weight

A number average molecular weight and a weight average molecular weightof a polymer were measured by GPC. Using HLC-8022GPC manufactured byTOSOH Corporation as an integrated-type apparatus of an ultravioletdetector and a differential refractometer and two TSK gel SuperHM-H(inner diameter: 6.0 mm, length: 15 cm) manufactured by TOSOHCorporation as a GPC column, a polystyrene equivalent number averagemolecular weight and weight average molecular weight were measured at asample concentration of 0.1% by weight, a flow rate of 0.2 mL/min, and atemperature of 40° C., using a N-methyl-2-pyrrolidone solvent (aN-methyl-2-pyrrolidone solvent containing 10 mmol/L of lithium bromide).

(4) Membrane Thickness

Using Model ID-C112 manufactured by Mitutoyo Corporation set to GraniteComparator Stand BSG-20 manufactured by Mitutoyo Corporation.

(5) Measurement of Crystallization Calorie by Differential ScanningCalorimetry (DSC)

A polymer electrolyte material (3.5 to 4.5 mg) as a specimen waspreliminarily dried at a temperature at which sulfonic acid group is notdecomposed (for example, 40 to 100° C.) to remove moisture, and then theweight is measured. In this case, since there is a possibility that achemical structure and a conformational structure of the polymer vary,the temperature should not raised to the temperature higher than thecrystallization temperature or thermal decomposition temperature. Aftermeasuring the weight, the polymer electrolyte material was subjected totemperature modulation differential scanning calorimetry in a firsttemperature rising stage under the following conditions.

DSC apparatus: DSC Q100 manufactured by TA Instruments Co.

Measuring temperature range: 25° C. to thermal decomposition temperature(for example, 310° C.)

Temperature raising rate: 5° C./min

Amplitude: +0.796° C.

Amount of sample: about 4 mg

Sample pan: crimp pan made of aluminum

Measuring atmosphere: nitrogen, 50 ml/min

Preliminary drying: vacuum drying at 60° C. for one hour

A value obtained by duplicating heat from the low temperature side to apeak top was calculated as a crystallization heat. Since the specimencontained moisture, the moisture content was calculated from detectedevaporation heat of moisture and then the weight of the polymerelectrolyte material was corrected. Enthalpy (or Heat) of evaporation ofwater is 2277 J/g.

Weight (g) of moisture in sample=Enthalpy of evaporation (J/g) ofmoisture of sample×amount (g.) of s ample/2277 (J/g)

Enthalpy of crystallization Correction Value (J/g)=Enthalpy ofcrystallization (J/g)×Amount (g) of Sample/(Amount of Sample−Weight (g)of Moisture in Sample)

(6) Measurement of the Degree of Crystallinity by Wide Angle X-RayDiffraction (XRD)

A polymer electrolyte material as a specimen was set to a diffractometerand X-ray diffraction was carried out under the following conditions.

X-ray diffractometer: RINT2500V manufactured by Rigaku Corporation

X-ray: Cu-Ka

X-ray output: 50 kV-300 mA

Optical system: concentration optical system

Scan speed: 20=20/min

Scan method: 20-0

Scan range: 20=5 to 600

Slit: divergence slit-½°, light receiving slit-0.15 mm, scatteringslit-½°

The degree of crystallinity was determined as follows: That is, eachcomponent was separated by profile fitting and a diffraction angle andan integrated intensity of each component were determined, and then thedegree of crystallinity was calculated from a calculation equation ofthe general formula (S2) using an integrated intensity of the resultingcrystalline peak and amorphous halo.

The degree of crystallinity (%)=(Sum of integrated intensity of entirecrystalline peak)/(Sum of integrated intensity of entire crystallinepeak and amorphous halo)×100   (S2)

(7) Visual Identification of Presence or Absence of Phase SeparationStructure

A sample of a membrane was immersed in pure water at 25° C. for 24 andtaken out in an atmosphere at 25° C. and a relative humidity of 50 to80%, and the presence or absence of a phase separation structure wasvisually identified.

(8) Observation of Phase Separation Structure by Transmission ElectronMicroscope (TEM)

A sample of a membrane was but into a piece of 5 mm×15 mm, and thissample piece was immersed in a 10 wt % solution of cesium acetate(solvent: ethanol) as a dyeing agent and was allowed to stand at 25° C.for 24 hours. The sample subjected a dyeing treatment was taken out andcut into a piece of 1 mm×5 mm, and the piece was embedded in a visiblelight curable resin and irradiated for 30 seconds with visible light tobe fixed.

A sample was sliced off at room temperature using a ultramicrotome, andthe resulting section was recovered on a Cu grid and subjected to TEMobservation. TEM observation was carried out at an accelerate voltage of100 kV and microphotographs were taken at 5000-fold, 20000-fold and50000-fold magnifications. As measuring apparatus, UltramicrotomeULTRACUT UCT (manufactured by Leica Microsystems AG) and TEM H-7650(manufactured by Hitachi, Ltd.) were used.

Further, with respect to image processing, processing of shadingcorrection, density conversion, and spatial filter was performed on TEMoriginal images in an automatic mode using LUZEX AP manufactured byNIRECO Corporation. Furthermore, processed images were expressed in 256tones of from black to white in an automatic mode of this apparatus. Inthe case where tones of 0 to 128 was defined as black color and tones of129 to 256 was defined as white color, measurement was performed withparameters of a circle equivalent diameter, a distance betweenparticles, a maximum length, a width of each layer and an interlayerdistance to determine an average interlaminar distance and an averagedistance between particles.

(9) Measuring Method of Purity

Quantitative analysis was carried out in the following conditions with agas chromatography (GC).

Column: DB-5 (manufactured by J&W) L=30 m φ=0.53 mm D=1.50 μm

Carrier: helium (line speed=35.0 cm/sec)

Analyzing condition

INJ. temp. 300° C.

Detct. temp. 320° C.

Oven 50° C. for 1 min

Rate 10° C./min

Final 300° C. for 15 min

SP ratio 50:1

(10) Resistance to Hot Water and Resistance to Hot Methanol

Resistance to hot water and resistance to hot methanol of an electrolytemembrane were evaluated by measuring a dimensional change ratio in anaqueous 30 wt % methanol solution at 60° C. The electrolyte membrane wascut into strips having a length of about 5 cm and a length of about 1 cmand, after immersing in water at 25° C. for 24 hours, the length (L1) ofeach strip was measured by a caliper. The electrolyte membrane wasimmersed in an aqueous 30 wt % methanol solution at 60° C. for 12 hoursand the length (L2) was measured again by a caliper, and then thedimensional change was visually observed.

Synthesis Example 1 Synthesis of 2,2-bis(4-hydroxyphenyl)-1, 3-dioxolanerepresented by the following general formula (G1)

Into a 500 ml flask equipped with a stirrer, a thermometer and adistillate tube, 49.5 g of 4,4′-dihydroxybenzophenone, 134 g of ethyleneglycol, 96.9 g of trimethyl orthoformate and 0.50 g of p-toluenesulfonicacid monohydrate were charged to be dissolved. Thereafter, the resultingsolution was kept at a temperature of 78 to 82° C. and stirred for 2hours. Furthermore, an internal temperature was gradually raised to 120°C. and heating was continued until distillation of methyl formate,methanol and trimethyl orthoformate completely ceases. This reactionsolution was cooled to room temperature and then diluted with ethylacetate, and an organic layer was washed with 100 ml of a 5% aqueoussolution of potassium carbonate and separated, and a solvent wasdistilled off. To a residue, 80 ml of dichloromethane was added toprecipitate a crystal and the resulting mixture was filtered and driedto obtain 52.0 g of 2,2-bis(4-hydroxyphenyl)-1,3-dioxolane. This crystalwas analyzed by gas chromatography to yield 99.8% of2,2-bis(4-hydroxyphenyl)-1,3-dioxolane and 0.2% of4,4′-dihydroxybenzophenone.

Synthesis Example 2 Synthesis of Disodium3,3′-disulfonate-4,4′-difluorobenzophenone represented by the followinggeneral formula (G2)

109.1 g of 4,4′-difluorobenzophenone (Aldrich reagent) was reacted at100° C. for 10 hours in 150 ml of a fuming sulfuric acid (50% SO3)(manufactured by Wako Pure Chemical Industries, Ltd.). Thereafter, thereactant was charged into a large amount of water little by little, andthe resulting mixture was neutralized with NaOH, and to this, 200 g ofcommon salt was added to precipitate a synthetic product. The resultingprecipitate was filtered and then recrystallized from an aqueous ethanolsolution to obtain disodium 3,3′-disulfonate-4,4′-difluorobenzophenonerepresented by the above general formula (G2). Purity was 99.3%. Thestructure was confirmed by ¹H-NMR. Impurities were quantitativelyanalyzed by capillary electrophoresis (organic matter) and ionchromatography (inorganic matter).

Example 1 (Polymerization of Prepolymer a1 Represented by the FollowingGeneral Formula (G3))

Into a 500 mL three-necked flask equipped with a stirrer, a nitrogenintroducing tube and a Dean-Stark trap, 13.82 g (Aldrich reagent, 100mmol) of potassium carbonate, 20.66 g (80 mmol) of K-DHBP obtained inthe above Synthesis Example 1, and 17.46 g (Aldrich reagent, 80 mmol) of4,4′-difluorobenzophenone were charged, and after the atmosphere in theflask was replaced by nitrogen, the resulting mixture was dehydrated at180° C. in 90 mL of N-methyl pyrrolidone (NMP) and 45 mL of toluene, andthe dehydrated content was heated to remove toluene and polymerizationwas carried out at 230° C. for 1 hour. The reaction solution waspurified by reprecipitating with a large amount of water to obtain aprepolymer al represented by the general formula (G3). The prepolymer alhad a weight average molecular weight of 50,000.

(Polymerization of Block Copolymer b1)

Into a 500 mL three-necked flask equipped with a stirrer, a nitrogenintroducing tube and a Dean-Stark trap, 6.91 g (Aldrich reagent, 50mmol) of potassium carbonate, 8.73 g (20 mmol) of the prepolymer al,10.33 g (40 mmol) of K-DHBP obtained in the above Synthesis Example 1,3.49 g (Aldrich reagent, 16 mmol) of 4,4′-difluorobenzophenone, and10.13 g (24 mmol) of disodium 3,3′-disulfonate-4,4′-difluorobenzophenoneobtained in the above Synthesis Example 2 were charged, and after theatmosphere in the flask was replaced by nitrogen, the resulting mixturewas dehydrated at 180° C. in 120 mL of N-methyl pyrrolidone (NMP) and 45mL of toluene, and the dehydrated content was heated to remove tolueneand polymerization was carried out at 230° C. for 10 hours. The reactionsolution was purified by reprecipitating with a large amount of water toobtain a block polymer b1. The block polymer b1 had a weight averagemolecular weight of 250,000.

The block polymer b1 is composed of a block (B2) of the prepolymer al inwhich the above general formula (G3) is a repeating unit and a block(B1) of a repeating unit which is composed of the above general formula(G1), benzophenone, and disulfonate in proportions of 10:4:6. A ratioW1/W2 of the block polymer b1 was 40 mmol/20 mmol, namely, 2.

A 25 wt % N-methyl pyrrolidone (NMP) solution, in which the resultingblock polymer b1 was dissolved, was pressure-filtered using a glassfiber filter and then applied and spread over a glass substrate. Afterdrying at 100° C. for 4 hours and heating to 300° C. over 30 minutesunder nitrogen, a heat treatment was carried out at 300° C. for 10minutes to obtain a polyketal ketone membrane (membrane thickness 30pm). The solubility of a polymer was extremely good. The resultingmembrane was immersed in 6N hydrochloric acid at 95□C. for 24 hours,subjected to proton substitution and deprotection reaction, and thensufficiently washed by immersing in a large excess amount of pure waterfor 24 hours to obtain polymer electrolyte membrane. The density of asulfonic acid group was 1.7 mmol/g.

In the resulting polymer electrolyte membrane, a crystallizationtemperature was recognized in DSC (the first heating stage) and acrystallization heat was 28.0 J/g. Also, a crystalline peak was notrecognized in wide angle X-ray diffraction (the degree of crystallinity0%). Since the polymer electrolyte membrane was an extremely toughelectrolyte membrane and formed a phase separation structure because itappeared to become opaque. Its proton conductivity was 110 mS/cm.Further, even when the membrane was immersed in hot water or hotmethanol, the membrane was neither dissolved nor collapsed and the rateL2/L1 of dimensional change was as small as 10%, and therefore themembrane was extremely excellent in resistance to hot water andresistance to hot methanol.

Moreover, a phase separation structure in which, an average interlaminardistance was 200 nm could be identified by TEM observations. Withrespect to a sea component, the component in a membrane thicknessdirection is four times larger than that of a membrane surface directionand anisotropy was recognized.

Example 2 (Polymerization of Prepolymer a2 Represented by the AboveGeneral Formula (G3))

In the same manner as in Example 1, except that a polymerization timewas changed from 1 hour to 1.5 hours, prepolymer a2 was obtained bypolymerization. The prepolymer a2 had a weight average molecular weightof 60,000.

(Polymerization of Block Copolymer b2)

In the same manner as in Example 1, except for charging 17.46 g (40mmol) of the prepolymer a2 in place o the prepolymer al, a polyketalketone polymer and a polymer electrolyte membrane were prepared. Thepolyketal ketone polymer had a weight average molecular weight of280,000. The solubility of the polymer was extremely good. A ratio W1/W2of the block polymer b2 was 1. The density of a sulfonic acid group ofthe resulting membrane was 1.4 mmol/g.

In the resulting polymer electrolyte membrane, a crystallizationtemperature was recognized in DSC (the first heating stage) and acrystallization heat was 33.2 J/g. Also, a crystalline peak was notrecognized in wide angle X-ray diffraction (the degree of crystallinity0%). Since the polymer electrolyte membrane was an extremely toughelectrolyte membrane and formed a phase separation structure because itappeared to become opaque. Its proto conductivity was 72 mS/cm. Evenwhen the membrane was immersed in hot water or hot methanol, themembrane was neither dissolved nor collapsed and the rate L2/L1 ofdimensional change was as small as 7%, and therefore the membrane wasextremely excellent in resistance to hot water and resistance to hotmethanol. Moreover, a phase separation structure in which an averageinterlaminar distance was 400 ran could be identified by TEMobservations.

Example 3

The polymer electrolyte membrane obtained in Example 2 was heated to270° C. in DSC and quenched and a sample of the polymer electrolytemembrane was taken out. In addition, 270° C. is a temperature at whichcrystallization proceeds but thermal decomposition does not occur. Thissample exhibited a crystallization heat of 0 when DSC was measuredagain. On the other hand, in wide angle X-ray diffraction (XRD), thedegree of crystallinity of 14% was observed. Also, by TEM observations,a phase separation structure in which an average interlaminar distanceis 40 nm can be identified.

Example 4 (Polymerization of Prepolymer a4 Represented by the AboveGeneral Formula (G3))

In the same manner as in Example 1, except that a polymerization timewas changed from 1 hour to 0.5 hour, a prepolymer a4 was obtained bypolymerization. The prepolymer a4 had a weight average molecular weightof 30,000.

(Polymerization of Block Copolymer b4)

In the same manner as in Example 1, except for charging 17.46 g (40mmol) of the prepolymer a4 in place of the prepolymer al, 3.46 g (25mmol) of potassium carbonate in place of 6.91 g (Aldrich reagent, 50mmol) of that, 5.17 g (20 mmol) of K-DHBP obtained in the aboveSynthesis Example 1, 1.75 g (Aldrich reagent, 8 mmol) of4,4′-difluorobenzophenone, and 5.06 g (12 mmol) of disodium3,3′-disulfonate-4,4′-difluorobenzophenone obtained in the aboveSynthesis Example 2, a polyketal ketone polymer and a polymerelectrolyte membrane were prepared. The polyketal ketone polymer had aweight average molecular weight of 320,000. The solubility of thepolymer was extremely good. A ratio W1/W2 of the block polymer b4 was0.5. The density of a sulfonic acid group of the resulting membrane was1.0 mmol/g.

In the resulting polymer electrolyte membrane, a crystallizationtemperature was recognized in DSC (the first heating stage) and acrystallization heat was 35.2 J/g. Also, a crystalline peak was notrecognized in wide angle X-ray diffraction (the degree of crystallinity0%). Since the polymer electrolyte membrane was an extremely toughelectrolyte membrane and formed a phase separation structure because itappeared to become opaque. Its proton conductivity was 41 mS/cm. Evenwhen the membrane was immersed in hot water or hot methanol, themembrane was neither dissolved nor collapsed and the rate L2/L1 ofdimensional change was as small as 2%, and therefore the membrane wasextremely excellent in resistance to hot water and resistance to hotmethanol. Moreover, a phase separation structure in which an averageinterlaminar distance was 120 nm could be identified by TEMobservations.

Example 5 (Polymerization of Prepolymer a54 Represented by the AboveGeneral Formula (G3))

In the same manner as in Example 1, except that a polymerization timewas changed from 1 hour to 1 hour and 10 minutes, a prepolymer a5 wasobtained by polymerization. The prepolymer a5 had a weight averagemolecular weight of 40,000.

(Polymerization of Block Copolymer b5)

In the same manner as in Example 1, except for charging 4.36 g (10 mmol)of the prepolymer a5 in place of the prepolymer al, 4.36 g (20 mmol) of4,4′-difluorobenzophenone in place of 3.49 g (Aldrich reagent, 16 mmol)of that, and 8.45 g (20 mmol) of disodium3,3″-disulfonate-4,4′-difluorobenzophenone obtained in the aboveSynthesis Example 2 in place of 10.13 g (24 mmol) of that, a polyketalketone polymer and a polymer electrolyte membrane were prepared. Theresulting polyketal ketone polymer had a weight average molecular weightof 210,000. The solubility of the polymer was extremely good. A ratioW1/W2 of the block polymer b5 was 4. The density of a sulfonic acidgroup of the resulting membrane was 1.7 mmol/g.

In the resulting polymer electrolyte membrane, a crystallizationtemperature was recognized in DSC (the first heating stage) and acrystallization heat was 27.5 J/g. Also, a crystalline peak was notrecognized in wide angle X-ray diffraction (the degree of crystallinity0%). Since the polymer electrolyte membrane was an extremely toughelectrolyte membrane and formed a phase separation structure because itappeared to become opaque. Its proton conductivity was 114 mS/cm. Evenwhen the membrane was immersed in hot water or hot methanol, themembrane was neither dissolved nor collapsed and the rate L2/L1 ofdimensional change was as small as 9%, and therefore the membrane wasextremely excellent in resistance to hot water and resistance to hotmethanol. Moreover, a phase separation structure in which an averageinterlaminar distance was 140 nm could be identified by TEMobservations. Comparative Example 1

A commercially available NAFION® 111 membrane (manufactured by DuPontCo.) was used to evaluate various properties. NAFION® 111 membrane wasimmersed in a 5% hydrogen peroxide water at 100° C. for 30 minutes,immersed in 5% dilute sulfuric acid at 100° C. for 30 minutes and thenadequately washed with deionized water at 100° C.

In the resulting polymer electrolyte membrane, a crystallizationtemperature was not recognized in DSC (first heating stage). Also, as aresult of wide angle X-ray diffraction, no crystalline peak wasrecognized. Since the polymer electrolyte membrane was visuallytransparent, a phase separation structure was not formed. Its protonconductivity was 80 mS/cm. Further, when the membrane was immersed inhot water or hot methanol, it swelled intensely and became difficult tohandle, and therefore it sometimes broke in picking up. The rate L2/L1of dimensional change was as large as 26%, and therefore the membranewas inferior in resistance to hot water and resistance to hot methanol.Moreover, a phase separation structure (cluster structure) in which anaverage interlaminar distance was 6 nm could be identified by TEMobservations.

Comparative Example 2 (Polymerization of Prepolymer c1 Represented bythe Following General Formula (G4))

Into a 500 mL three-necked flask equipped with a stirrer, a nitrogenintroducing tube and a Dean-Stark trap, 13.82 g (Aldrich reagent, 100mmol) of potassium carbonate, 2-1.47 g (80 mmol) of 1, 1-bis(4-hydroxyphenyl) cyclohexane, and 17.46 g (Aldrich reagent, 80 mmol) of4,4′-difluorobenzophenone were put, and after the atmosphere in theflask was replaced by nitrogen, the resulting mixture was dehydrated at180° C. in 90 mL of N-methyl pyrrolidone (NMP) and 45 mL of toluene, andthe dehydrated content was heated to remove toluene and polymerizationwas carried out at 230° C. for 1 hour. The reaction solution waspurified by reprecipitating with a large amount of water to obtain aprepolymer c1 represented by the general formula (G4). The prepolymer c1had a weight average molecular weight of 50,000.

(Polymerization of Block Copolymer d1)

Into a 500 mL three-necked flask equipped with a stirrer, a nitrogenintroducing tube and a Dean-Stark trap, 6.91 g (Aldrich reagent, 50mmol) of potassium carbonate, 8.94 g (20 mmol) of the prepolymer c1,10.73 g (40 mmol) of 1,1-bis(4-hydroxyphenyl)cyclohexane, 2.18 g(Aldrich reagent, 10 mmol) of 4,4′-difluorobenzophenone, and 12.67 g (30mmol) of disodium 3,3′-disulfonate-4,4′ difluorobenzophenone obtained inthe above Synthesis Example 2 were charged, and after the atmosphere inthe flask was replaced by nitrogen, the resulting mixture was dehydratedat 180° C. in 120 mL of N-methyl pyrrolidone (NMP) and 45 mL of toluene,and the dehydrated content was heated to remove toluene andpolymerization was carried out at 230° C. for 10 hours. The reactionsolution was purified by reprecipitating with a large amount of water toobtain a block polymer d1. The block polymer d1 had a weight averagemolecular weight of 250,000. A ratio W1/W2 of the block polymer d1 was2.

A 25 wt % N-methyl pyrrolidone (NMP) solution, in which the resultingblock polymer d1 was dissolved, was pressure-filtered using a glassfiber filter and then applied and spread over a glass substrate. Afterdrying at 100° C. for 4 hours and heating to 300° C. over 30 minutesunder nitrogen, a heat treatment was carried out at 300° C. for 10minutes to obtain a membrane (membrane thickness 30 μm). The solubilityof a polymer was extremely good. The membrane was immersed in a largeexcess amount of pure water for 24 hours and then sufficiently washed toobtain a polymer electrolyte membrane. The density of a sulfonic acidgroup of the resulting membrane was 1.9 mmol/g.

In the resulting polymer electrolyte membrane, a crystallizationtemperature was not recognized in DSC (first heating stage). Also, acrystalline peak was not recognized in wide angle X-ray diffraction (thedegree of crystallinity 0%). Since the resulting polymer electrolytemembrane had only such low strength that the membrane is broken whenpicked up with tweezers and formed a phase separation structure becauseit appeared to become opaque. Its proton conductivity was 118 mS/cm.Further, when the membrane was immersed in hot water or hot methanol, itswelled intensely and the rate L2/L1 of dimensional change was 56%, andtherefore the membrane was inferior in resistance to hot water andresistance to hot methanol. Moreover, a phase separation structure inwhich an average interlaminar distance was 200 nm could be identified byTEM observations.

Comparative Example 3

In the same manner as in Example 1, except that the charge amount of20.66 g (80 mmol) of K-DHBP obtained in the above Synthesis Example 1was changed to 17.1 g (80 mmol) of DHBP, a polyetherketone polymer wasobtained by polymerization. From the initial stage of thepolymerization, a polymer was precipitated and the polymerization washardly carried out. Since the polymer was insoluble in a solvent,polymerization of a block polymer was difficult.

Comparative Example 4

Into a 500 mL three-necked flask equipped with a stirrer, a nitrogenintroducing tube and a Dean-Stark trap, 13.82 g (Aldrich reagent, 100mmol) of potassium carbonate, 20.66 g (80 mmol) of K-DHBP obtained inthe above Synthesis Example 1, 12.2 g (Aldrich reagent, 56 mmol) of4,4′-difluorobenzophenone, and 10.1 g (24 mmol) of disodium3,3′-disulfonate-4,4′-difluorobenzophenone obtained in the aboveSynthesis Example 2 were charged, and after the atmosphere in the flaskwas replaced by nitrogen, the resulting mixture was dehydrated at 180°C. in 100 mL of N-methyl pyrrolidone (NMP) and 50 mL of toluene, and thedehydrated content was heated to remove toluene and polymerization wascarried out at 230° C. for 6 hours. The reaction solution was purifiedby reprecipitating with a large amount of water to obtain a polyketalketone random copolymer. The polyketal ketone random copolymer had aweight average molecular weight of 250,000.

Next, a polymer electrolyte membrane was prepared by the methoddescribed in Example 1. A ratio W1/W2 of the membrane becomes 1/0. Thedensity of a sulfonic acid group of the resulting membrane was 0.9mmol/g. Since the resulting membrane was transparent, a phase separationstructure was not recognized visually. The membrane was excellent indimensional stability, but it was inferior in proton conductivity toExample 1. Moreover, by TEM. observations, a pattern in which an averagedistance between particles was 6 nm could be identified, but a phaseseparation structure having an interlaminar distance of 10 nm or more,shown in the definition of the present invention, could not identified.

Comparative Example 6 (Polymerization of Prepolymer a6 Represented bythe Following General Formula (G5))

Into a 500 mL three-necked flask equipped with a stirrer, a nitrogenintroducing tube and a Dean-Stark trap, 13.82 g (Aldrich reagent, 100mmol) of potassium carbonate, 20.66 g (80 mmol) of K-DHBP obtained inthe above Synthesis Example 1, and 19.2 g (Aldrich reagent, 88 mmol) of4,4′-difluorobenzophenone were charged, and after the atmosphere in theflask was replaced by nitrogen, the resulting mixture was dehydrated at180° C. in 90 mL of N-methyl pyrrolidone (NMP) and 45 mL of toluene, andthe dehydrated content was heated to remove toluene and polymerizationwas carried out at 210° C. for 1 hours. The reaction solution waspurified by reprecipitating with a large amount of water and aprepolymer a6 represented by the general formula (G5) was obtained bywashing the precipitate with hot methanol. An average of N3 is 10 andthe prepolymer a6 had a number average molecular weight of 5,000.(Polymerization of block copolymer b6)

Into a 500 mL three-necked flask equipped with a stirrer, a nitrogenintroducing tube and a Dean-Stark trap, 8.29 g (Aldrich reagent, 60mmol) of potassium carbonate, 11.36 g (44 mmol) of K-DHBP obtained inthe above Synthesis Example 1, and 16.89 g (40 mmol) of disodium3,3′-disulfonate-4,4′-difluorobenzophenone obtained in the aboveSynthesis Example 2 were charged, and after the atmosphere in the flaskwas replaced by nitrogen, the resulting mixture was dehydrated at 180°C. in 90 mL of N-methyl pyrrolidone (NMP) and 45 mL of toluene, and thedehydrated content was heated to remove toluene and polymerization wascarried out at 210° C. for 1 hour to obtain a prepolymer. The resultingprepolymer had a number average molecular weight of 7,000.

Next, 17.46 g (40 mmol) of prepolymer a6 and 20 mL of toluene wereadded, and the resulting mixture was dehydrated at 180° C. again, andthe dehydrated content was heated to remove toluene and polymerizationwas carried out at 230° C. for 8 hours to obtain a block polymer b6. Theresulting block polymer b6 had a weight average molecular weight of235,000.

The block polymer b6 is composed of a block (B2) of the prepolymer al inwhich the above general formula (G5) is a repeating unit and a block(B1) of a repeating unit which is composed of the above general formula(G1) and disulfonate-benzophenone in proportions of 1:1. A ratio W1/W2of the block polymer b6 is 20 mmol/20 mmol, namely, 1.

A 25 wt % N-methyl pyrrolidone (NMP) solution, in which the resultingblock polymer b6 was dissolved, was pressure-filtered using a glassfiber filter and then applied and spread over a glass substrate. Afterdrying at 100° C. for 4 hours and heating to 300° C. over 30 minutesunder nitrogen, a heat treatment was carried out at 300° C. for 10minutes to obtain a polyketal ketone membrane (membrane thickness 30μm). The solubility of a polymer was extremely good. The membrane wasimmersed in 6N hydrochloric acid at 95° C. for 24 hours, subjected toproton substitution and deprotection reaction, and then was immersed ina large excess amount of pure water for 24 hours and then sufficientlywashed to obtain a polymer electrolyte membrane. The density of asulfonic acid group of the resulting membrane was 2.1 mmol/g.

In the resulting polymer electrolyte membrane, a crystallizationtemperature was recognized in DSC (the first heating stage), and acrystallization heat was 26.8 J/g. Also, a crystalline peak was notrecognized in wide angle X-ray diffraction (the degree of crystallinity0%). Since the polymer electrolyte membrane was an extremely toughelectrolyte membrane and formed a phase separation structure because itappeared to become opaque. Its proton conductivity was 120 mS/cm. Evenwhen the membrane was immersed in hot water or hot methanol, themembrane was neither dissolved nor collapsed and the rate L2/L1 ofdimensional change was as small as 11%, and therefore the membrane wasextremely excellent in resistance to hot water and resistance to hotmethanol. Moreover, a phase separation structure in which an averageinterlaminar distance was 18 nm could be identified by TEM observations.

Comparative Example 7 (Polymerization of Prepolymer a7 Represented bythe Above General Formula (G5))

In the same manner as in Example 6, except that the charge amount of4,4′-difluorobenzophenone was changed to 18.33 g (Aldrich reagent, 84mmol), a prepolymer a7 represented by the general formula (G5) wasobtained. An average of N3 is 20 and the resulting prepolymer a7 had anumber average molecular weight of 10,000.

(Polymerization of Block Copolymer b7)

In the same manner as in Example 6, except that the charge amount of11.36 g (44 mmol) of K-DHBP obtained in the above Synthesis Example 1was changed to 10.85 g (42 mmol), a prepolymer was obtained. Theresulting prepolymer had a number average molecular weight of 14,000.

Next, 17.46 g (40 mmol) of prepolymer a6 and 20 mL of toluene wereadded, and the resulting mixture was dehydrated at 180° C. again, andthe dehydrated content was heated to remove toluene and polymerizationwas carried out at 230° C. for 8 hours to obtain a block polymer b7. Theblock polymer b7 had a weight average molecular weight of 255,000. Aratio W1/W2 of the block polymer b7 was 20 mmol/20 mmol, namely, 1.

A polymer electrolyte membrane was prepared by the method described inExample 6 to obtain a polyketal ketone membrane (membrane thickness 30um). The solubility of the polymer was' extremely good. The density of asulfonic acid group of the resulting membrane was 2.1 mmol/g.

In the resulting polymer electrolyte membrane, a crystallizationtemperature was recognized in DSC (the first heating stage), and acrystallization heat was 34.1 J/g. Also, a crystalline peak was notrecognized in wide angle X-ray diffraction (the degree of crystallinity0%). Since the polymer electrolyte membrane was an extremely toughelectrolyte membrane and formed a phase separation structure because itappeared to become opaque. Its proton conductivity was 131 mS/cm. Evenwhen the membrane was immersed in hot water or hot methanol, themembrane was neither dissolved nor collapsed and the rate L2/L1 ofdimensional change was as small as 13%, and therefore the membrane wasextremely excellent in resistance to hot water and resistance to hotmethanol. Moreover, a phase separation structure in which an averageinterlaminar distance was 40 nm could be identified by TEM observations.Comparative

Example 8 (Polymerization of Prepolymer a8 Represented by the AboveGeneral Formula (G5))

In the same manner as in Example 6, except that the charge amount of4,4′-difluorobenzophenone was changed to 17.89 g (Aldrich reagent, 82mmol), a prepolymer a8 represented by the general formula. (G5) wasobtained. An average of N3 is 40 and the prepolymer a7 had a numberaverage molecular weight of 20,000.

(Polymerization of Block Copolymer b8)

In the same manner as in Example 6, except that 7.63 g of 4,4′-biphenol(manufactured by TOKYO CHEMICAL INDUSTRY Co., Ltd., 41 mmol) was used inplace of 11.36 g (44 mmol) of K-DHBP obtained in the above SynthesisExample 1, a prepolymer was obtained. The prepolymer had a numberaverage molecular weight of 29,000.

Next, 17.46 g (40 mmol) of ‘prepolymer a8 and 20 mL of toluene wereadded, and the resulting mixture was dehydrated at 180° C. again, andthe dehydrated content was heated to remove toluene and polymerizationwas carried out at 230° C. for 8 hours to obtain a block polymer b8. Theblock polymer b8 had a weight average molecular weight of 245,000. Aratio W1/W2 of the block polymer b8 was 20 mmol/20 mmol, namely, 1.

A polymer electrolyte membrane was prepared by the method described inExample 6 to obtain a polyketal ketone membrane (membrane thickness 30pm). The solubility of the polymer was extremely good. The density of asulfonic acid group of the resulting membrane was 2.1 mmol/g.

In the resulting polymer electrolyte membrane, a crystallizationtemperature was recognized in DSC (the first heating stage), and acrystallization heat was 22.4 J/g. Also, a crystalline peak was notrecognized in wide angle X-ray diffraction (the degree of crystallinity0%). Since the polymer electrolyte membrane was an extremely toughelectrolyte membrane and formed a phase separation structure because itappeared to become opaque. Its proton conductivity was 144 mS/cm. Evenwhen the membrane was immersed in hot water or hot methanol, themembrane was neither dissolved nor collapsed and the rate L2/L1 ofdimensional change was as small as 14%, and therefore the membrane wasextremely excellent in resistance to hot water and resistance to hotmethanol. Moreover, a phase separation structure in which an averageinterlaminar distance was 110 nm could be identified by TEMobservations.

Comparative Example 9 (Polymerization of Prepolymer a9 Represented bythe Above General Formula (G5))

In the same manner as in Example 6, except that the charge amount of4,4′-difluorobenzophenone was changed to 20.95 g (Aldrich reagent, 96mmol), a prepolymer a9 represented by the general formula (G5) wasobtained. An average of N3 is 5 and the resulting prepolymer a9 had anumber average molecular weight of 3,000.

(Polymerization of Block Copolymer b9)

In the same manner as in Example 6, except that 8.94 g of 4,4′-biphenol(manufactured by TOKYO CHEMICAL INDUSTRY Co., Ltd., 48 mmol) was used inplace of 11.36 g (44 mmol) of K-DHBP obtained in the above SynthesisExample 1, a prepolymer was obtained. The resulting prepolymer had anumber average molecular weight of 4,000.

Next, 17.46 g (40 mmol) of prepolymer a8 and 20 mL of toluene wereadded, and the resulting mixture was dehydrated at 180° C. again, andthe dehydrated content was heated to remove toluene and polymerizationwas carried out at 230° C. for 8 hours to obtain a block polymer b9. Theblock polymer b9 had a weight average molecular weight of 271,000. Aratio W1/W2 of the block polymer b9 was 20 mmol/20 mmol, namely, 1.

A polymer electrolyte membrane was prepared by the method described inExample 6 to obtain a polyketal ketone membrane (membrane thickness 30pm). The solubility of the polymer was extremely good. The density of asulfonic acid group of the resulting membrane was 2.1 mmol/g.

In the resulting polymer electrolyte membrane, a crystallizationtemperature was recognized in DSC (the first heating stage), and acrystallization heat was 20.1 J/g. Also, a crystalline peak—was notrecognized in wide angle X-ray diffraction (the degree of crystallinity0%). Since the resulting polymer electrolyte membrane was an extremelytough electrolyte membrane and formed a phase separation structurebecause it appeared to become opaque. Its proton conductivity was 121mS/cm. Even when the membrane was immersed in hot water or hot methanol,the membrane was neither dissolved nor collapsed and the rate L2/L1 ofdimensional change was as small as 10%, and therefore the membrane wasextremely excellent in resistance to hot water and resistance to hotmethanol. Moreover, a phase separation structure in which an averageinterlaminar distance was 10 nm could be identified by TEM observations.

Comparative Example 10

A membrane was evaluated as a reverse osmosis membrane. In this example,a salt removal rate was determined by measuring a salt concentration ofa supplied solution and a salt concentration of a permeated solution andsubstituting the resulting measurements into the following equation:

Salt removal rate (%)={1−(salt concentration of permeatedsolution)/(salt concentration of supplied solution)}×100.

Further, water permeability was expressed by a water quantity (m³/m²·d)passed through a membrane per unit time (day) and unit area (m²).

A cloth-reinforced polysulfone support membrane (ultrafiltrationmembrane) which is used as a microporous support membrane was producedby the following technique. That is, a wet nonwoven fabric with a sizeof 30 cm long and 20 wide, which comprises mixed fiber of polyesterfiber of 0.5 dtex in finess of single yarns and polyester fiber of 1.5dtex in finess of single yarns and has permeability of 0.7 cm³/cm²-secand an average pore size of 7 μm or less, was fixed onto a glass plate,and a dimethylformamide (DMF) solution (2.5 poise: 20° C.) having 15% byweight of polysulfone was casted thereon in such a way that an overallthickness is 200 μm, and the resulting glass plate was immediatelyimmersed in water to prepare a microporous support membrane ofpolysulfone.

Next, a 25% by weight n-methylpyrrolidone (NMP) solution of the blockpolymer b6 obtained in Example 6 was applied onto the obtainedmicroporous support membrane of polysulfone to form a functional layerhaving a thickness of 1 μm.

A complex semipermeable membrane thus obtained was subjected to areverse osmosis test under the conditions of 0.5 MPa and 25° C. using a0.2% by weight sodium chloride aqueous solution adjusted to a pH 6.5 asa raw water. Consequently, the water permeability was 0.60 m³/m²·d andsodium chloride removal rate was 97.0%, and this membrane exhibited afunction as a reverse osmosis membrane.

INDUSTRIAL APPLICABILITY

The polymer electrolyte material and the polymer electrolyte membrane ofthe present invention can be applied for various electrochemicalapparatus, for example, fuel cell, water electrolysis apparatus andchloroalkali electrolysis apparatus, and are preferably for a fuel cell,particularly preferably for fuel cell, using an aqueous hydrogen ormethanol solution as a fuel.

The application of the polymer electrolyte fuel cell of the presentinvention is not particularly limited, and is preferably used as powersupply sources for portable devices such as cellular phone, personalcomputer, PDA, video cameras, and digital cameras; household appliancessuch as cordless cleaners; toys; mobile objects, for example, vehiclessuch as electric bicycle, motorcycle, automobile, tjus, and trucks,marine vessels, and railroads; substitutions of conventional primary andsecondary cells, such as stationary type power generator; andcombinations of these fuel cells with a hybrid power supply.

1. A polymer electrolyte material including a constituent unit (A1)containing an ionic group and a constituent unit (A2) substantially notcontaining an ionic group, wherein a phase separation structure isobserved by a transmission electron microscope and a crystallizationheat measured by differential scanning calorimetry is 0.1 J/g or more,or a phase separation structure is observed by a transmission electronmicroscope and the degree of crystallinity measured by wide angle X-raydiffraction is 0.5% of more.
 2. The polymer electrolyte materialaccording to claim 1, wherein the polymer electrolyte material is anionic group-containing block copolymer composed of a block (B1)containing an ionic group and a block (B2) substantially not containingan ionic group and a ratio W1/W2 of a molar amount W1 of B1 to a molaramount W2 of B2 is 0.2 or more and 5 or less.
 3. The polymer electrolytematerial according to claim 1, wherein the ionic group-containingcopolymer is an aromatic polyetherketone-type polymer.
 4. The polymerelectrolyte material according to claim 2, wherein the block (B2)substantially not containing an ionic group comprises a constituent unitrepresented by the following general formula (Q1):

Z¹ and Z² in the general formula (Q1) represent a divalent organic groupcontaining an aromatic ring and each of Z¹ and Z² may represent two ormore kinds of groups but does not substantially contain an ionic group;and a and b each independently represents a positive integer.
 5. Thepolymer electrolyte material according to claim 4, wherein the Z¹ insaid general formula (Q1) is a phenylene group and the Z² in saidgeneral formula (Q1) is at least one selected from the following generalformulas (X-1), (X-2), (X-4) and (X-5):

the groups represented by the general formula (X-1), (X-2), (X-4) or(X-5) may be optionally substituted with a group other than the ionicgroup.
 6. The polymer electrolyte material according to claim 4, whereinthe Z¹ and the Z² in the general formula (Q1) are a phenylene group. 7.The polymer electrolyte material according to claim 1, wherein saidionic group is a sulfonic acid group
 8. The polymer electrolyte materialaccording to claim 1, wherein the density of the sulfonic acid group ofthe block (B1) containing an ionic group is 1.7 to 5.0 mmol/g and thedensity of the sulfonic acid group of the block (B2) substantially notcontaining an ionic group is to 0.5 mmol/g.
 9. The polymer electrolytematerial according to claim 1, wherein the block (B1) containing anionic group comprises constituent units represented by the followinggeneral formulas (P1) and (P2):

in the general formulas (P1) and (P2), A represents a divalent organicgroup containing an aromatic ring and M¹ and M² represent hydrogen, ametal cation, or an ammonium cation; and A may represent two or morekinds of groups.
 10. The polymer electrolyte material according to claim9, wherein said A is' at least one kind of constituent unit selectedfrom the following general formulas (X-1) to (X-7):

the groups represented by the general formulas (X-1) to (X-7) may beoptionally substituted.
 11. A method for producing a polymer electrolyteform article composed of an ionic group-containing block copolymer,having a block (B1) containing an ionic group and a block (B2)substantially not containing an ionic group, in which a ratio W1/W2 ofweight W1 of the B1 to weight W2 of the B2 is 0.2 or more and 5 or less,wherein a polymer electrolyte material formed by introducing protectivegroups into at least the block (B2) substantially not containing anionic group is formed and then at least a portion of the protectivegroups contained in the form article is deprotected.
 12. A polymerelectrolyte form article, which is composed of the polymer electrolytematerial according to claim
 1. 13. A membrane electrode assembly, whichis composed of the polymer electrolyte material according to claim 1.14. A polymer electrolyte fuel cell, which is composed of the polymerelectrolyte material according to claim
 1. 15. The polymer electrolytematerial according to claim 4, wherein the block (B2) substantially notcontaining an ionic group comprises a constituent unit represented byone of the following general formula (Q2-Q7):


16. A polymer electrolyte form article comprising a polymer electrolytematerial comprising an ionic group-containing block copolymer comprisinga block (B1) containing an ionic group and a block (B2) substantiallynot containing an ionic group, wherein the block (B2) comprises aprotecting group that is removable from the polymer electrolyte formarticle, wherein the polymer electrolyte form article has a formcomprising a membrane form, a plate-like form, a fiber-like form, or ahollow fiber-like form.
 17. The polymer electrolyte form article ofclaim 16, wherein the polymer electrolyte form article allowspenetration of an acid solution.
 18. The polymer electrolyte formarticle of claim 16, wherein the protecting group is removable at roomtemperature.
 19. The polymer electrolyte form article of claim 16,wherein the protecting group is removable by an aqueous solution. 20.The polymer electrolyte form article of claim 16, wherein the blockcopolymer comprises ketal.
 21. The polymer electrolyte form article ofclaim 16, wherein the removal of the protecting group comprisesgenerating a ketone group.
 22. The polymer electrolyte form article ofclaim 16, wherein the polymer electrolyte material comprises polyetherketoneketone, polyetherether ketone, polyetherether ketoneketone,polyether ketone ether ketoneketone, or polyether ketone sulfone. 23.The polymer electrolyte form article of claim 16, wherein the polymerelectrode form article comprises a polymer electrolyte materialcomprising an ionic group-containing block copolymer comprising a block(B1) containing an ionic group and a block (B2) substantially notcontaining an ionic group, wherein the polymer electrolyte material hasa phase separation structure, wherein the polymer electrolyte materialhas a crystallization heat of 0.1 J/g or more, or a degree ofcrystallinity of 0.5% or more, wherein the block (B1) containing anionic group comprises constituent units represented by the followinggeneral formulas (P1):

in the general formulas (P1), A represents a divalent organic groupcontaining an aromatic ring and M³ and M⁴ represent hydrogen, a metalcation, or an ammonium cation; and A may represent two or more kinds ofgroups: wherein said A is at least one kind of constituent unit selectedfrom the following general formulas (X-3):

wherein the block (B2) substantially not containing the ionic groupcomprises a constituent unit represented by a general formula (Q1):

wherein (i) Z1 and Z2 independently represents a divalent organic groupcomprising one or more aromatic rings; and a and b each independentlyrepresent a positive integer; and (ii) Z1 and Z2 do not substantiallycontain an ionic group, wherein the block (B1) and/or the block (B2) hasa formula weight of 2000 or more.
 24. The polymer electrolyte formarticle of claim 16, wherein the polymer electrolyte form article has aform comprising a membrane form.
 25. The polymer electrolyte formarticle of claim 24, wherein the membrane form comprises a film and afilm-shaped article.
 26. The polymer electrolyte form article of claim16, wherein the polymer electrolyte material has a phase separationstructure, wherein the polymer electrolyte material has acrystallization heat of 0.1 J/g or more, or a degree of crystallinity of0.5% or more, wherein the block (B2) substantially not containing theionic group comprises a constituent unit represented by a generalformula (Q1):

wherein (i) Z1 and Z2 independently represents a divalent organic groupcomprising one or more aromatic rings; and a and b each independentlyrepresent a positive integer; and (ii) Z1 and Z2 do not substantiallycontain an ionic group, wherein the block (B1) and/or the block (B2) hasa formula weight of 2000 or more.
 27. The polymer electrolyte materialaccording to claim 16, wherein the block (B2) substantially notcontaining an ionic group comprises a constituent unit represented byone of the following general formula (Q2-Q7):


28. The polymer electrolyte form article of claim 16, wherein the ionicgroup has a negative charge.
 29. The polymer electrolyte form article ofclaim 16, wherein the ionic group has a proton exchange capability. 30.The polymer electrolyte form article of claim 16, wherein the polymerelectrolyte material is resistant to hydrolysis.